St. Mirren Otoo began his career in the youth side for
Sporting St. Mirren at the age of 16. He signed his first professional football contract with St. Mirren in 2007 when he was 16 and made an instant impact in the team. They were in the
Ghana Division One League when he joined them in the 2007–08 season. His key striking abilities and performances qualified St. Mirren to the
Premiership for the first time in the club's history. His brace against Fair Point on the final day of the league secured the Division One Zone III title and sealed their qualification. He was the club's top scorer and second top scorer in the National Division One league. When the team qualified to the GPL for the first time he was registered as one of their senior squad members when he was 16 years old on 30 October 2008. He earned the discovery player of the season award in the 2008–09 season after he won five man of the match awards and got 5 goals from 15 games for his club.
Hearts of Oak Otoo signed for the 2009–2010 season with
Accra Hearts of Oak SC on a 3-year deal. He finished his debut season with the club with 10 league goals in 19 matches and a consecutive individual title winning the Ghana Premier League's best player of the season. In September 2010, he moved to Tunisian club
Esperance Sportive de Tunis on a 4-month loan deal worth $150,000. He was initially set to join the club on a permanent deal for a deal worth $500,000 however it was renegotiated into a loan deal. He scored a hat-trick, which was the first in 2012–13 season in the 5–2 win over
New Edubiase. Otoo scored a brace against
Berekum Arsenal. Otoo renewed his contract with Accra Hearts of Oak for another season in May 2013. Otoo scored a hat-trick against
Tema Youth on the final game of the season and win the top scorer of
Ghana Premier League with 20 goals. At the end of the season, he was adjudged the Ghana Premier League best player for the second time and the SWAG Premier League player of the year. He ended the season as the club's second top goal scorer with 13 league goals and 15 goals in all competitions trailing only to
Kristian Opseth who scored 16 league goals and 17 goals in all competition. He left the club on 1 January 2017. ==International career==