The new service comes on the back of the successful addition of Windows Live Messenger (formerly MSN) to 3s Internet portfolio last year. 3 customers have sent over 133 million messages via Windows Live Messenger in the last 12 months.
Yahoo Messenger will be available for free on selected handsets to all of 3s pay monthly customers. 3 Pay As You Go customers will also be able to access the service until the end of 2007.
3 marketing director John Penberthy-Smith said: Now 2 million Yahoo! Messenger users can enjoy the exclusive benefit of free instant messaging on 3.