How to Integrate OptinMonster with Mailchimp

This connector is on every OptinMonster plan. Official page: How to Connect OptinMonster with Mailchimp. Attach MonsterLeads as a backup.

1. Create an API key in Mailchimp (Mailchimp's own key guide).

2. In the campaign builder, open Integrations, search for Mailchimp.

3. Enter an internal account name and the API key. Click Connect to Mailchimp.

4. Under Email Provider Lists, pick the Audience. Required.

5. Optional: leave Enable Double Opt-in? on (the default) or turn it off for single opt-in. Optional: pick tags that already exist on that Audience.

6. Save.

Turning off double opt-in does not flush the pending queue. Addresses captured while it was on still wait for the confirm click.

Mailchimp groups

Groups have to exist in Mailchimp first.

Automatic: Integrations → Mailchimp → add a Group Label (not shown to visitors) → set Groups Selection Type to Hidden → tick the groups every new lead should join.

Visitor-picked: same panel, set the type to Visible. The label shows on the form. Use checkboxes for multiple groups or radio buttons for one. You can reorder, pre-tick or hide options.

Test with a unique address every time. Mailchimp will not re-subscribe an unsubscribed or deleted address through the API. For that path, embed a Mailchimp-hosted form with the Form Embed block.

A "merge fields were invalid" error usually means Mailchimp requires FNAME (or similar) and the campaign does not send it. Either add the field or turn off the required flag in Mailchimp. Phone numbers only land if the merge tag is literally PHONE.

More connectors: OptinMonster integrations.