The third-year defensive back was entering the final season of his contract. Terms of the deal were not disclosed Sunday.
Robey signed with the Bills as an undrafted free agent out of Southern Cal in April 2013 and has not missed a game for Buffalo.
In 32 games and eight starts, Robey has four sacks and an interception.
He has played primarily as a nickel back. Buffalo drafted cornerback Ronald Darby with its first pick, 50th overall, in April's draft.