How can I merge duplicate contacts in Outlook?

There is MAPILab Duplicates Remover for Outlook, which is not free, but not expensive. I've not used it, but i think the free trial version will only work for 10 contacts at a time, if it is anything like..

...Duplicate Email Remover from MAPILab, which I have used, and which worked very well.

EDIT: Having looked a bit closer at that add-on, it seems that you can choose which fields it uses to detect duplicates, but all you can do is flag or delete them, and not merge them.

The best thing I can think of is for you to export all your contacts into Excel through a CSV file, where you can manipulate them so that fields are copied across the different entries, and then delete the dupes. It will take some time and effort, but at least it will be easier on a spreadsheet.

What I ended up doing was create a new contacts folder. Copy and paste your entire contacts list to this folder. Then simply select all of the contacts in the new folder and paste them back to the original contacts folder.

As they are copied you will be asked to Crete duplicates or update existing contacts. Choose to update existing. I have over 1000 contacts and this process worked for all but a few contacts.

You can try out Scrubly which is a service that helps you manage your contacts.

Scrubly`s features:

• Remove duplicate contacts
• Easily merge and resolve conflicts
• Eliminate duplicates across folders
• Powerful algorithm for safe, quick and thorough scans
• Automatically backs up your address book. Safe storage you can access and download any timein the future
• Safely revert your data back to its original condition at any point in the process. You have complete control

Check out this official support document: http://support.microsoft.com/kb/299349

This procedure changed with the 2010 version, so make sure to look at the second set of instructions. This can be applied to many elements of outlook, so you can just limit it to contacts.

Outlook 2010

1. In Outlook 2010, select the folder for which you want to delete duplicate items.
2. Click the View tab in the Ribbon, click Change View in the Ribbon, and then click to change the folder view to a table type view. For example, click the List icon.
3. Right-click a column heading, and then click Field Chooser.
4. From the list at the top of the Field Chooser, click to select the All fields .
5. Drag the Modified field to the table heading.
6. Verify that the duplicate items have a unique date from the original set of items. If it is unique, click the Modified heading so that the items are sorted by this field.
7. Click the first item in the set that you want to delete, scroll to the last item in the set that you want to delete, and then click the last item while you hold down the SHIFT key.
8. Press DELETE to permanently delete all selected items.

Did you attempt anything yet?