The pitch process also included MediaCom and Dentsu Aegis.
As part of the first review of its own advertising, Twitter UK has also today named Lucky Generals as its first retained creative agency in the UK.
David Wilding, planning director at Twitter, was part of the team of UK and US leaders to appoint the agency. Wilding joined the social media network from PHD last year, after an acclaimed tenure that culminated in him sweeping the media awards in 2014 as part of the team behind the Lego TV ad campaign.
He said: "It was a fascinating process and we'd like to genuinely thank every agency who took part for their passion and thinking.
"We're hugely excited about working with Lucky Generals and PHD on our consumer marketing activity."
The appointment of PHD follows Dick Costolo's announcement that he would step down as Twitter's chief executive on 1 July amid increasing pressure to prove the company's commercial model is robust enough to hit its stated targets.
Costolo is being replaced, in the interim, by Twitter's co-founder and chairman Jack Dorsey.