The agency beat WCRS, Bartle Bogle Hegarty, Delaney Lund Knox Warren & Partners and M&C Saatchi in a pitch handled through the AAR.
The pitch, which was run by 3's UK marketing team and included members of the global brand team, was conducted in less than two weeks.
TBWA's presentation, which was led by the joint managing director Matt Shepherd-Smith, included an alternative creative route from the "open your eyes" strapline introduced last month. 3 is yet to make a decision on which creative strategy to go forward with. However, it is likely that the existing campaign will be modified.
The Independent Television Commission recently upheld complaints about TBWA's "football" spot for 3, following viewer complaints that the video sequences in the ad were of a higher quality than the service was able to achieve. It was banned from future transmission in its current form.
Last month, 3 promoted its director of consumer marketing, Graeme Oxby, to marketing director, taking over from Lisa Gernon, who launched the brand in the UK. Gernon has reverted to her original role as a consultant.
3 has struggled to attract customers since its much-delayed launch in March, with TBWA's multimillion-pound campaign failing to capture the imagination of the public.
A 3 UK statement said: "Following the review, we are pleased to confirm TBWA\ London as our above-the-line agency of record."
Trevor Beattie, the chairman and creative director at TBWA\London, said: "I've never seen the agency so galvanised as in the past two weeks. Retaining 3 meant the world to us and we're chuffed to bits that we are still working together."
MindShare's hold on the 3 media planning and buying account is unaffected by the review.