O2 customers will be able to receive free text alerts from Twitter from August.
The deal allows O2 customers to receive tweets from chosen friends, @mentions (tweets referring to an individual's name) and direct messages via SMS. They can also send and reply to tweets, which will be charged at the normal rate.
O2 said over a million customers a month access social networking sites like Twitter and Facebook, and hundreds of thousands have downloaded social networking applications.
Antony Douglas, head of content at O2, said, "We believe that mobile will soon become the most popular way of accessing social networking sites, giving real-time access to tweets and status updates wherever you are."