Oluseyi Smith was part of the 4x100m relay team in his first Olympic Games at London 2012. The team of Smith, Jared Connaughton, Gavin Smellie, and Justyn Warner finished the race in bronze-medal position, but was later disqualified due to a lane violation.
Smith was selected for the 4x100m team after finishing in third place at the Canadian Track and Field Championships in the 100m event with a personal best time of 10.22s.
Smith was named an alternate to the 4x100m relay team at the 2011 World Championships in Korea. Smith competed at the 2006 World Junior Championships reaching the semifinal in the 100m and competed at the 2003 World Youth Championships in Sherbrooke, Quebec where he finished sixth in the long jump and reached the semifinal in the 200m.