How to Merge Two Office 365 Tenants: A Step-by-Step Tutorial

Written By Adom James
Updated on August 18th, 2025

William Miller Query: “Our company has acquired another business, and we now have two separate Office 365 accounts (tenants). We want to combine everything, including emails, OneDrive, Teams, etc., into one place. So our employees can work together securely. What’s the simple method to merge two Office 365 tenants without losing any data?”

Introduction: Each tenant holds its own set of users, emails, files, and collaboration tools like Teams and SharePoint. Using two Office 365 tenants side by side can create hectic, increase costs, and make it harder for employees to collaborate efficiently. That’s why many users want to combine two Office 365 tenants. In this blog, we will discuss the best methods to merge two Microsoft Office 365 tenancies without losing any data. You can also use the Office 365 Backup Tool. directly. It helps move your data from one Office 365 account to another without any hassle.

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Table of Contents

Why Businesses Need to Merge Two Tenants Office 365?

Merging two tenants becomes necessary in several situations, such as:

Company mergers or acquisitions.
Internal restructuring.
Simplifying IT infrastructure.
Reducing licensing and management costs.
Creating a unified communication system.

Keeping two tenants separate leads to inefficiencies and duplicated costs. It also results in poor collaboration across teams. A merger improves overall productivity and data control.

Pre-Migration Planning: To Merge Two Office 365 Tenants

Preparation is important for a quick and 100% safe result. Here’s what you should do before the actual migration:

Decide which tenant will be the main (target) one and which will be merged into it.
Create a list of everything that you need: mailboxes, OneDrive files, SharePoint sites, Teams data, etc.
Check that the domain(s) used in the source tenant can be added to the target tenant after migration.
Moreover, always backup your data before starting the migration to avoid any data loss.

Manual Method to Merge Two Office 365 Tenants

To merge a small amount of data. A manual merge using Microsoft 365 Admin Center and PowerShell can be a cost-effective option. This method involves several steps and requires technical skills to perform. Here is how you can perform it:

Step 01: Create Users in the Target Tenant

Firstly, log in to the Microsoft 365 Admin Center.
Now, go to Users > Active Users > Add a User.
Create new accounts for users from the source tenant.

Step 02: Remove the Domain from the Source Tenant

Unassign the domain from all users, distribution groups, and aliases.
Change user UPNs (User Principal Names) to a temporary domain (e.g., @yourcompany.onmicrosoft.com).
After that, delete related DNS records from your domain registrar.

Step 03: Add Domain to the Target Tenant

In the Admin Center of the target tenant, go to Settings > Domains.
Next, click Add Domain and enter the domain name.
Verify the domain using a TXT record in your DNS settings.

Step 04: Update User Information in the Target Tenant

Change email addresses and UPNs to the newly added domain.
Further, reconfigure aliases and group email addresses.

Step 05: Update MX Records

Lastly, add the correct MX record in the target tenant to route incoming emails to the new destination.

Note: This manual process does not migrate emails, files, Teams chats, or calendar entries. You’ll need to manually export/import this data or use PowerShell scripts for complete migration.

Alternative Manual Method: Merge Two Office 365 Tenants

This method is used for a large amount of data. Also, it allows both tenants to operate in parallel, which offers flexibility but also increases complexity.

Firstly, sign in to the Microsoft Entra Admin Center of the target tenant.
Now, navigate to External Identities > Cross-tenant access settings.
After that, click on Default settings, then:

Enable inbound access to allow users from the source tenant to access apps and resources.
Enable outbound access to allow users in the target tenant to access the source tenant.

Now, go to Organizational settings and click Add organization.
Then, enter the domain name of the source tenant and press Add.
Further, configure both inbound and outbound settings for the added accounts.
In the end, save the changes to apply the cross-tenant access configuration.

Professional Way to Merge Two Office 365 Tenants

For a quick and reliable solution, you can use the CloudMigration Office 365 Backup Tool. This tool is specifically designed to transfer all your data from one Office 365 account to another. It supports migration of shared mailboxes and public folders. Generally, this utility offers 100% accurate Office 365 Tenant-to-Tenant Migration without data loss or minimal disruptions. Moreover, it preserves original data formatting, structure, and metadata.

How to Connect Two Office 365 Tenants?

Primarily, download the CloudMigration Office 365 Backup Tool.
Now, provide your Office 365 login credentials to sign in.
After that, choose the mailbox folder to migrate.
Select Office 365 as the Saving Format from the list.
Next, enter your Office 365 details [ID & Password].
Lastly, apply advanced features and click Convert.

Important Note: This tool also allows you to migrate Office 365 to IMAP Server as well as various other file types and email clients.

Conclusion

In this complete blog post, we discussed several methods to merge two Office 365 tenants. If you choose any of the methods, firstly, read the preparation points. Because it helps you to get a 100% accurate result. The manual method is best for both small and large data. However, they contain multiple limitations. Therefore, using a professional tool is strongly recommended. This tool securely transfers all your data from one Microsoft 365 account to another.

Frequently Asked Questions

Q1. Is it possible to merge only the contacts between two Office 365 tenants without combining all the data?

Ans: Yes, you can selectively migrate contacts using a professional CloudMigration Office 365 Backup Tool or export/import contacts manually via CSV files. This allows contact sharing without merging entire data sets.

Q2. Can Office 365 tenants be merged following a company merger?

Ans: Absolutely. This is one of the most common reasons for merging tenants. Using migration tools or hybrid setups, companies can unify their environments post-merger to improve collaboration and IT efficiency.

About The Author:

Adom James