The 26-year-old has agreed fresh terms that will keep him at the Exiles until at least the end of the 2013/2014 season.
Ojo, who has won two England caps, has scored 56 tries in 145 appearances for Irish. He was part of the Churchill Cup-winning England Saxons team during the summer.
Irish head coach Toby Booth said: "Topsy has been a highly consistent player for this club over a number of seasons now, and his commitment to the shirt and to his team-mates is second to none.
"He is a tremendous attacker with ball in hand and an outstanding defender.
"His try-scoring record for the club speaks for itself, and we are certainly very pleased that he has decided his immediate future is with London Irish."