How to Migrate Mailchimp to HubSpot (Without Losing Data or Breaking Your Segments)

Published on June 11, 2026

If you’re reviewing how your CRM handles contact data after the move, Alltomate’s CRM automation service covers post-migration setup. Start with a free business process audit to map what needs to change before you start.

Mailchimp and HubSpot CRM are not structurally equivalent tools. Mailchimp organises contacts around audiences — each with its own list logic, its own suppression state, its own unsubscribe records. HubSpot organises them around a CRM object model: contacts, companies, deals, with list logic built on top of a shared database. That structural difference is why a migration that looks simple on the surface — export CSV, import CSV — regularly produces broken segments, missing properties, and unsubscribes that don’t carry over correctly.

This guide covers the full migration path: what to decide before you start, how to export cleanly from Mailchimp, how to handle field mapping inside HubSpot, and what to watch for in the 48 hours after import. Whether you’re planning to migrate or simply evaluating whether to switch from Mailchimp to HubSpot, understanding the structural differences between the platforms is critical. It also covers what’s worth automating once you’re live — because the move itself is only half the work.

What Most Migrations Get Wrong From the Start

The default assumption going into this migration is that it’s a data transfer problem. Export the list, clean it up, import it. That assumption is what causes most of the failures we see after the fact.

Mailchimp stores contacts inside audiences. Each audience is its own suppression universe — an unsubscribe in Audience A doesn’t automatically apply to Audience B. As explained in Mailchimp’s official documentation, suppression lists are maintained separately for each audience rather than globally across an account. HubSpot uses a single contact database with subscription-type logic layered on top. When you import contacts from multiple Mailchimp audiences into HubSpot without accounting for that structural difference, you end up with contacts who had legitimately unsubscribed from your list now sitting in HubSpot as marketable — because the unsubscribe record was audience-specific and didn’t survive the flattening into a single contact database.

In implementations we’ve built for clients moving from Mailchimp to HubSpot, this is consistently the first thing that breaks — not the import itself, but the suppression state of contacts after it. The fix isn’t complicated, but it has to be handled before the import, not patched after.

The second common failure is treating Mailchimp tags and groups as equivalent to HubSpot contact properties. They aren’t. Mailchimp tags are flat labels. HubSpot properties are typed fields with defined values — text, dropdown, date, number. If you import a column of comma-separated tags as a single text property in HubSpot, you lose the ability to filter and segment on those values individually. That mismatch is invisible during the import. It only surfaces weeks later when someone tries to build a workflow or send a segmented email, and discovers the underlying data structure doesn’t support what they need.

The structural difference is easier to understand visually. The diagram below shows why Mailchimp audience-level suppression logic often breaks when multiple audiences are consolidated into HubSpot’s single contact database.

Decisions to Make Before You Export Anything

There are four decisions that determine the shape of your migration. Making them before you touch the export will save you a second import.

1. How many audiences are you migrating? If you have more than one Mailchimp audience, decide whether you’re merging them into a single HubSpot contact database or maintaining logical separation through lists or properties. HubSpot doesn’t support multi-audience isolation the way Mailchimp does. If your audiences were intentionally separate — different brands, different business units, different products — you need a property or static list strategy in HubSpot to replicate that separation before the first contact lands.

2. What custom fields need to survive the move? Map every Mailchimp merge field to a HubSpot contact property before the import. For fields that have no direct equivalent in HubSpot’s default property set, create custom contact properties in HubSpot first, with the correct type set. Importing before those properties exist means the data either gets dropped or lands in a field you can’t use for segmentation or workflow logic.

3. What is your unsubscribe and suppression strategy? Export your unsubscribed contacts from each Mailchimp audience as a separate file. In HubSpot, use this to set the marketing email opt-out status on those contacts — either by importing the suppression file separately or by mapping the subscription status field during the main import. This is not optional if you operate in regions covered by CAN-SPAM, GDPR, or equivalent frameworks.

4. Are you migrating automations? Mailchimp automations do not transfer. As shown in HubSpot’s migration documentation, Mailchimp contact records are included in the migration mapping, while automation logic and workflow configuration are not. They need to be rebuilt as HubSpot workflows. Treat that as a separate project that follows the contact migration. Trying to rebuild automations and migrate data simultaneously is where timelines fall apart and data issues get obscured by the noise of everything moving at once.

For a deeper look at the system logic behind CRM automation decisions — including how to think about workflow architecture after a platform move — the CRM automation guide covers the underlying structure.

If you’re evaluating implementation support during the migration, HubSpot maintains a directory of vetted solutions providers. You can review Alltomate’s HubSpot Solutions Partner profile for details on migration, CRM automation, and post-implementation workflow services.

How to Export Your Data From Mailchimp

Mailchimp provides two export paths: a full audience export and a segmented export. For migration purposes, you want both — the full audience export to capture all contacts and their merge field data, and separate exports filtered by subscription status so you can handle subscribed, unsubscribed, and cleaned contacts distinctly in HubSpot.

To export, go to Audience → All Contacts → Export Audience. This produces a CSV with all merge fields, subscription status, member rating, and the date each contact was added. If you have multiple audiences, repeat this for each one and keep the files clearly named by audience.

Before importing into HubSpot, the CSV needs to be cleaned:

• Remove Mailchimp-specific columns that have no equivalent in HubSpot — Member Rating, Latitude, Longitude, GMTOFF, DSTOFF, CC — unless you’re creating custom properties to hold them
• Separate contacts by subscription status into distinct files: subscribed, unsubscribed, non-subscribed, cleaned
• Standardise phone number formats if they vary across records — HubSpot’s import accepts inconsistent formats, but the inconsistency creates cleanup work later
• Check for duplicate email addresses across multiple audience exports if you’re merging audiences into a single HubSpot database

The cleaned-contacts file — contacts marked as hard bounced or spam complaints — should not be imported as marketable. Import them separately with opt-out status set, or exclude them from the main import and hold them for suppression use only.

One of the most common mistakes we see at this stage is importing a single mixed-status export into HubSpot and planning to separate contacts later. That usually results in unsubscribed and cleaned contacts entering the same import process as active subscribers, creating avoidable suppression and compliance work after the migration. Separating contacts by subscription status before import is significantly easier than correcting subscription state after the fact.

This export structure is illustrated below. Separating subscription states before import prevents suppression and compliance issues from being carried into HubSpot.

Importing Into HubSpot — Where Field Mapping Breaks

HubSpot’s import tool is straightforward until you hit the field mapping step. That’s where most migrations lose data silently. The import completes successfully, the record count matches, no error appears — and the problem only surfaces weeks later when someone tries to build a filter or workflow using a field that didn’t map correctly.

Before importing, create all custom contact properties you need underSettings → Properties → Contact Properties. Set the correct property type for each — text, number, dropdown, date — because a field imported as text cannot be used for date-based filtering or number-based workflow conditions later. The property type is structural; you can’t retroactively change it without data loss.

During the import, HubSpot will ask you to map each CSV column to a contact property. Three specific points where mappings fail:

Email address as deduplication key. HubSpot uses email as the default identifier. If a contact already exists in HubSpot with the same email, the import will update that record rather than create a duplicate. This is usually correct, but if you’re importing into a HubSpot account that already has contacts, review which fields will be overwritten before you run the import.

Subscription status mapping. Map your Mailchimp subscription status column to HubSpot’s email opt-out property or the relevant marketing email subscription type during the import step. If you skip this mapping, imported contacts will not have their Mailchimp opt-out status applied automatically. This is the most consequential field to get right and the one most commonly left unmapped.

List assignment on import. HubSpot allows you to add contacts to a static list as part of the import. Use this to tag each import batch by source — for example, “Mailchimp Migration — June 2026” — so you can audit, isolate, or correct the batch after the fact if something needs fixing.

A consistent pattern we see in this setup is clients discovering mid-import that a custom field they relied on in Mailchimp has no clean equivalent in HubSpot. The warning sign is usually a Mailchimp column containing multiple values in a single cell — tags, interests, or group memberships separated by commas — that later need to be filtered individually. The workaround — stuffing those values into a single text field — looks acceptable at the contact level but breaks every downstream filter and workflow that needs to act on those values individually. The better move is to pause the import, create the correct property type, and restart.

The field-mapping problem usually appears when Mailchimp values are forced into the wrong HubSpot property type. The comparison below shows the difference between a structurally correct and incorrect mapping approach.

What Breaks After the Import (And Why)

The import completes. The contact count looks right. And then, over the next 48 hours, three things surface.

Segments behave unexpectedly. HubSpot’s active lists work on real-time property evaluation. If imported properties have formatting inconsistencies, incorrect types, or blank fields, contacts will fall out of lists they should be in — or stay in lists they shouldn’t. Check your most critical active lists the day after import by pulling the criteria and manually auditing a sample of contacts against it. Active list membership discrepancies are almost always traceable to import data quality, not HubSpot logic errors.

Existing workflows fire incorrectly or not at all. Any HubSpot workflow with an enrollment trigger based on imported contact properties may fire on the entire imported batch — or not fire at all if the trigger value doesn’t match what was imported. Pause your existing workflows before the import, then re-evaluate enrollment criteria and test on a small segment before activating at full scale. This is especially important for lifecycle stage triggers, which can move contacts backward as well as forward.

Email subscription state conflicts across subscription types. HubSpot supports multiple subscription types — marketing emails, one-to-one emails, product updates, and others. If you mapped a single Mailchimp opt-out status to a single HubSpot subscription type, that suppression only applies to that type. A contact who unsubscribed from Mailchimp’s general marketing emails could still receive HubSpot product update emails unless all relevant subscription types are set.

We saw this directly in a SaaS client migration that looked clean by every metric — correct record count, all fields mapped, no import errors. After their first HubSpot send, a segment of previously unsubscribed contacts received an email. The root cause was a subscription type mismatch: opt-out had been applied to the marketing email type, but the send was executed under a different subscription category that had defaulted to opted-in on import. The data transfer was correct; the subscription logic was not. The fix was a one-time bulk update across affected contacts, but it came after a send — not before.

The issue below illustrates how a migration can appear successful while still exposing contacts to emails they should no longer receive.

For post-migration data cleanup — including how to sequence corrections without creating new inconsistencies — the CRM data cleanup strategies guide covers the right order of operations. Teams dealing with recurring quality issues often implement CRM cleanup automation rather than relying on manual audits.

What to Automate Once You’re Live in HubSpot

Once the migration is stable, the structure HubSpot provides makes a range of automations practical that either weren’t possible in Mailchimp or required constant manual intervention. The migration is the threshold. What you build after it determines the return on making the move. If you’re new to the concept, this overview of CRM automation explains how automated workflows improve data quality, lead management, and reporting after a platform migration.

Lifecycle stage transitions. HubSpot’s contact properties and workflow logic allow you to move contacts through lifecycle stages — subscriber to lead to MQL to SQL — based on behaviour: page views, form fills, email engagement, deal activity. Mailchimp can trigger emails based on activity, but it cannot update a contact’s stage in a way that integrates with a sales pipeline or routes contacts to the right team. This is the structural difference that makes the migration worthwhile for most B2B teams, and lifecycle automation is the first workflow category worth building. Many of these workflows fall into common CRM automation use cases that become practical once contact data is centralized in a single CRM.

Automated contact sync from external systems. If contact data enters your business through forms, booking tools, payment processors, or other platforms, setting up automated sync into HubSpot prevents the manual import cycle from restarting. The automated contact sync approach covers this: new contacts enter HubSpot directly from source systems, with properties mapped and lifecycle stage set at entry, so the database reflects what’s actually happening in your business without someone maintaining it manually. This also helps teams reduce CRM manual entry across sales and marketing operations.

Re-engagement and list hygiene. Contacts that have been sitting in a Mailchimp list for two or three years arrive in HubSpot with unknown engagement levels. Rather than emailing the full imported list and absorbing deliverability hits, build a re-engagement workflow that routes cold contacts through a short confirmation sequence before adding them to active marketing sends. This is especially important if a significant portion of your imported contacts had non-subscribed status — they were never opted in, never opted out, and are effectively an unknown deliverability risk.

For clients who’ve gone through a similar migration and built automation on top of it, the compounding effect becomes visible over the first few months. Alltomate worked with a B2B services firm that completed a platform migration and then built lifecycle automation on top — the result was a system where leads moved from initial capture to sales-qualified status without manual CRM updates at any stage. Organizations that want to eliminate this maintenance burden often automate CRM updates across their customer lifecycle. That implementation is documented in the CRM migration and sales automation case study.

FAQs

Can I migrate my Mailchimp automations directly to HubSpot?

No. Mailchimp automations cannot be exported and do not transfer to HubSpot in any form. The logic can usually be replicated, but the sequences, triggers, delays, and conditional branches need to be reconfigured manually inside HubSpot’s workflow builder. Treat automation rebuild as a separate project that follows the contact migration — not something to run concurrently. Mixing both at the same time makes it harder to isolate what’s causing problems if something goes wrong.

Will my Mailchimp unsubscribes carry over to HubSpot automatically?

Not automatically. Mailchimp stores unsubscribe data per audience in your export CSV as a subscription status column. During the HubSpot import, you must explicitly map that column to HubSpot’s email opt-out field or the relevant marketing email subscription type. If you skip that mapping, imported contacts will not have their Mailchimp opt-out status applied automatically. This is the most consequential mapping in the entire import.

Do I need to keep Mailchimp running while I migrate?

Yes, until the migration is fully validated. Keep Mailchimp active so you have a reference point if anything looks wrong in HubSpot after the import. Most migrations can be validated within 48 to 72 hours — checking segment counts, subscription states, and running a test send. Once you’ve confirmed everything is working correctly in HubSpot, you can cancel or downgrade your Mailchimp plan.

How long does a Mailchimp to HubSpot migration take?

For a single Mailchimp audience with under 10,000 contacts and a small number of custom fields, the technical steps — export, clean, map, import, verify — take a few hours. The planning decisions (field mapping strategy, subscription logic, audience consolidation) take longer depending on the complexity of your Mailchimp setup. Migrations involving multiple audiences, significant custom field structures, and automation rebuild can span several working days across multiple sessions.

Will I lose my Mailchimp email campaign history after the move?

Yes. Mailchimp campaign history — send stats, opens, clicks at the campaign level — does not transfer to HubSpot. HubSpot’s official migration documentation only includes contact records in its Mailchimp migration mapping. Export and archive your Mailchimp campaign reports before the migration. Once the account is cancelled or downgraded, historical reporting access may be limited.

About the author

Miguel Carlos Arao is the Founder & CEO of Alltomate, a Zapier Certified Platinum Solution Partner and HubSpot Solutions Partner focused on Mailchimp-to-HubSpot migration workflows, including contact field mapping, list segmentation transfer, and post-migration CRM automation. The patterns in this article come directly from building and troubleshooting Mailchimp-to-HubSpot migration systems across client engagements in SaaS onboarding and B2B sales operations.

View Alltomate’s HubSpot Solutions Partner profile for additional implementation details and platform expertise.

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