Anthony Annan began playing football with a local colts Super Rainbow Stars in Cape Coast, Ghana. He also played for Cape Coast Venomous Vipers in the Ghanaian Division one league before joined Sekondi Hasaacas in 2003 and later moved to Accra Hearts of oak in 2005. At Accra Hearts of Oak, Annan was regarded as the best young midfielder in Ghana. He combined midfield artistry with some goal scoring skills, and endeared himself to many football fans in Ghana. Anthony Annan joined Accra Hearts of Oak from Sekondi Hasaacas FC in the 2005–06 league season.
He signed for the Norwegian club I.K. Start in January 2007, after a very promising career in Ghana with his local club Accra Hearts of Oak. He quickly established himself as a first team regular during I.K. Start's preseason games, and showed skills both on and off the ball. Unfortunately he was plagued by injury and illness during the first part of the 2007 season, and did not gain trust from then head coach Benny Lennartson in the important final games to avoid relegation.
After Start got relegated during the 2007 season, he joined Stabæk on loan until August 2008. He had been playing well in the heart of midfield as Stabæk went unbeaten in an impressive opening half of the season. Stabæk hinted that they want to buy him from Start, but Start stated that they would have to pay a "European transfer-fee". Instead, Annan claimed that several "big" clubs had approached his agent and that he would leave Norway during the summer.
On 1 August 2008, it was revealed that Annan would be travelling to England for a trial with Blackburn Rovers. After impressing Paul Ince and the Blackburn coaching staff immensely, while on trial, he was sent back to his club to play in one more competitive game where the Blackburn Rovers scouts were to watch and report back on whether or not to complete the signing.
On 31 August 2008, he was presented for the audience on Lerkendal as a Rosenborg player before the match against Vålerenga. Rosenborg paid £1.2 million to get him from Start. (Rosenborg won the game against Vålerenga 2–1). He made his league debut for Rosenborg on 14 September 2008 against Fredrikstad, with the game ending 1–1.
A Junior and Olympic International for Ghana, Annan received his first senior call up for the national team on 20 March 2007 as a direct injury replacement for Essien for Ghana's FIFA International friendlies against Austria and Brazil in 2007. His first cap came against Brazil on 27 March 2007 at the Råsunda Stadium, Stockholm, Sweden when Ghana lost 0–1. He made his first goal for the national team in the 2–2 draw against Mali 15 November 2009. He played for Ghana at the 2010 FIFA World Cup in South Africa.
^"Stars fall to Love strike". Official Website (Ghana Football Association). 27 March 2007. Retrieved 29 March 2007. "Ghana coach, Claude Le Roy had the opportunity to try out four uncapped players as he handed Anthony Annan a place in the starting line up in his debut game for the Black Stars."