Starcom picked up the account from MindShare without a pitch, after P&G's £32 billion acquisition of the shaving giant earlier in the year.
However, media planning is expected to remain with its incumbent agencies around the world in the short term.
P&G may now mirror this move by moving Gillette's creative from the Omnicom-owned incumbent, BBDO.
Gillette spends £23 million in the UK annually, according to Nielsen Media Research.
It was already expected that planning and buying would be moved out of MindShare after the agency won the £700 million planning and buying account for P&G's main competitor, Unilever.
The acquisition of Gillette brands such as Mach3, Duracell, Oral-B and Braun will create the world's largest consumer goods company and because of this, the deal was reliant on the US government giving regulatory approval.
The Federal Trade Commission eventually agreed to the deal provided that P&G sell Gillette's Right Guard deodorant and Rembrandt tooth-whitening businesses.