He joined Royal Antwerp FC in January 2007 where he became a first team regular, and he helped Antwerp qualify for the playoffs, finishing second. On 30 August 2008, it was announced that Utaka would join Danish club OB.
Utaka joined Danish side OB in 2008. In his first season he finished joint fourth place on the scorers list, while he led all scorers in his second season. He finished with 18 goals in 33 matches, the first time in five years an OB player was top scorer in the league (last was Steffen Højer in 2004–05 with 20 goals).
On 21 September 2009, national coach Shaibu Amodu selected Peter for the Nigerian national football team. Utaka made his debut for Nigeria months later in a 5–2 home win over Congo DR on 3 March 2010, despite only getting his call up late after the NFF called his mother looking for him. He scored the first goal and assisted on the second. He scored twice against in a Nations Cup qualifier against Ethiopia.