Competitors will take to their bicycles for the first stages of the famous race - in the capital and Kent - in early July.
Four is understood to have beaten Pitch PR, brandRapport and M&C Saatchi Sports & Entertainment to the account.
TfL chief press officer (operations) Stuart Ross said it was hoped the event would ‘give a boost to' cycling in London.
The transport body is working with Mayor Ken Livingstone and VisitLondon to promote the race and showcase the capital as a city capable of hosting ‘world-class events'.
TfL is using the ExCel centre in Docklands as its media base during the UK stages of the competition (PRWeek, 8 Sep).
