If you have switched jobs, combined old backups, or simply collected several PST files over the years, you have probably felt the same frustration: your mail history is scattered across files, and searching for one email means opening each file separately. Merging those PST files into a single, unified file solves this. This guide walks through how to merge multiple PST files into one, using both Outlook’s own tools and a faster automated method, while keeping every folder, email, and attachment intact.
Quick answer
To merge multiple PST files into one, open Outlook, add each PST file as a data file through File, then Open and Export, then Open Outlook Data File. Then drag the folders from each extra file into the folders of your main PST, or use the Import and Export wizard to import one file into another. For many files, large mailboxes, or files that are damaged, a dedicated PST merge tool is faster and safer, since it combines everything in one pass, keeps your folder structure, and avoids duplicate or missed items.
Why merge PST files into one?
A PST file (Personal Storage Table) stores your Outlook emails, contacts, calendars, and attachments in a single portable file. Over months and years it is easy to end up with several of them, from old backups, previous jobs, archived projects, or exported mailboxes. If you want a refresher on how this file differs from the offline OST file, see our guide on the difference between OST and PST files.
Merging them into one file brings real benefits:
- One search, all your mail. You stop hunting across separate files for the same conversation.
- Simpler backups. One file to back up and protect instead of several.
- Cleaner organization. Folders and subfolders sit together instead of being split across files.
- Easier migration. A single consolidated file is simpler to move to a new computer or import into Microsoft 365.
Before you merge: what to check first
A little preparation avoids most problems.
- Back up every PST file you plan to merge, by copying them to another folder or drive, before you touch anything.
- Check each file opens cleanly in Outlook. A corrupt file should be repaired before merging, since combining a damaged file can spread the problem into your main PST.
- Note the combined size. If merging will push the result close to the PST size limit, plan to keep some files separate or export by date range instead.
- Decide on your main file. Pick the PST you will merge everything into, so your folder structure stays predictable.
How to merge multiple PST files into one
Method 1: Add each PST as a data file, then drag folders across
This is the simplest way for two or three files.
- In Outlook, go to File, then Open and Export, then Open Outlook Data File.
- Browse to the extra PST file and click OK. It appears as a separate file in your folder list on the left.
- Repeat for every PST file you want to merge.
- Click a folder inside one of the added files, then drag it onto the matching folder in your main PST. Outlook copies the items across.
- Repeat for every folder in every added file, then confirm the items appear correctly in your main PST.
Method 2: Import one PST into another with the Import and Export wizard
Importing folds one file’s contents into another in a single pass, which is tidier than dragging folder by folder.
- Go to File, then Open and Export, then Import/Export.
- Choose Import from another program or file, then click Next.
- Select Outlook Data File (.pst), then click Next.
- Browse to the PST file you want to merge in, choose how duplicates should be handled, and click Next.
- Pick the destination folder, which should be the matching top level folder in your main PST, then click Finish.
- Repeat for each additional PST file.
Method 3: Merge folder by folder to avoid duplicates
If your PST files overlap, for example two backups from around the same time, merge deliberately rather than importing everything at once.
- Open both files as data files in Outlook.
- Sort each folder by date or subject so you can compare contents quickly.
- Move or copy only the items that are missing from your main PST.
- Once you are confident nothing is duplicated, remove the now empty extra data file from Outlook without deleting the underlying file, keeping it as a backup.
Method 4: Merge automatically with a professional PST tool
Manual merging works, but it gets slow and error prone once you have more than a couple of files, large mailboxes, or any file that will not open cleanly in Outlook. An automated approach solves this directly.
A professional PST Converter can add multiple PST files at once, merge their contents into a single output file, and preserve the original folder structure and metadata, all without relying on Outlook staying open and stable through a long drag and drop process. This is the more reliable option when you are consolidating several years of mailboxes or merging files from more than one person. Once merged, you can open the result directly in Outlook, or, if you need to hand a copy to someone without Outlook installed, see our guide on how to open a PST file without Outlook.
What if one of the PST files is corrupt?
Do not merge a damaged file as it is, since the corruption can carry over into your main PST. Repair it first. For light damage, Microsoft’s built in Inbox Repair Tool can help, though it has real limits, and our guide on what to do when SCANPST.exe is not working covers what to try when it fails. For files that will not open at all or that SCANPST cannot fix, a dedicated recovery tool repairs the structure so the file is safe to merge.
What if the merged file gets too large?
Combining several PST files can push the result close to Outlook’s size limit, which sits around 50 GB by default in modern versions. If that happens, keep the merged file lean by archiving older mail out of it, or split it back into smaller, organized files. Our guide on how to split a large PST file covers exactly that, so you can merge for organization and then split again by year or project if the file grows unwieldy.
How to keep your PST files organized going forward
- Settle on one main PST file per mailbox instead of letting new ones accumulate.
- Archive older mail into clearly labelled files rather than creating scattered exports.
- Back up your merged file on a regular schedule.
- Review your data files occasionally and merge or retire old ones before they pile up again.
Conclusion
Merging multiple PST files into one turns scattered, hard to search mail into a single, organized mailbox. For a couple of files, adding them as data files and dragging folders across, or using the Import and Export wizard, works well. For several files, large mailboxes, or anything already showing signs of damage, a dedicated PST tool merges everything faster and more safely. Back up first, repair any damaged files before combining them, and keep an eye on the final size, and you will end up with one clean file that holds your complete mail history.
Frequently Asked Questions
Yes. Add each PST file as a data file through File, then Open and Export, then Open Outlook Data File, and then either drag folders into your main PST or use the Import and Export wizard to import one file into another.
It can, if the files overlap in date range or content. The Import and Export wizard lets you choose how duplicates are handled, and for overlapping backups it is safer to compare folders and move only the missing items rather than importing everything at once.
Outlook itself does not set a strict limit on how many data files you can add, but merging many files manually becomes slow and easy to get wrong. A dedicated PST tool that merges several files in one pass is far more practical once you are past two or three.
Yes, with a dedicated PST merge tool. It reads the files directly and combines them into one output file without needing Outlook to be installed or running.
The damage can carry into your main file, so repair the corrupt PST before merging. Try the Inbox Repair Tool for minor issues, and a PST recovery tool when that does not work.
No. Merging combines mail data, contacts, and calendar items. It does not change your account settings, signatures, or rules, which live in your Outlook profile rather than inside the PST file itself.
After merging, open each folder in your main PST and compare the item counts against the original files. For large merges, sorting by date helps you quickly spot anything that did not come across.
- How to Fix Outlook Error 0x80070057 (The Parameter Is Incorrect) - August 9, 2026
- How to Fix Outlook Error 0x800CCC0F (Connection to Server Interrupted) - August 8, 2026
- How to Merge Multiple PST Files Into One - August 7, 2026