Gyan began his professional career aged 17, initially playing for Liberty Professionals in Acra, Ghana. The young striker made an impressive start to his career, scoring eleven goals in sixteen appearances, before he was quickly snapped up by Italian side Udinese in 2003. He debuted for the Bianconeri that season, but couldn't break into the first team; thus he was sent on loan to Modena in Serie B from 2004 to 2006. The Ghanaian did moderately well there, scoring 15 times in two seasons.
During this period, Gyan broke into Ghana's national side set up, making his debut in 2003 and scoring on debut against Somalia in a World Cup qualifier. Ghana made it to the 2006 tournament in Germany, where Gyan scored a penalty against the Czech Republic. This international attention brought fresh speculation about whether Gyan would stay in Italy or leave for a bigger club. Gyan eventually returned to Udinese in 2006, playing two seasons in Serie A before moving to France.
Stade Rennais moved to buy Gyan in 2008, for a Ã¢â€šÂ¬8 million fee. He scored fourteen times in Ligue 1 and became a popular player at the club, but in 2010 Gyan was purchased again, this time by English Premier League team Sunderland. This was partially due to the rise in fame of Gyan, who was the most prominent hero, and perhaps villain of Ghana's quarter-final run in the 2010 World Cup in South Africa. He scored three goals as Ghana progressed through the tournament, but he missed a critical penalty in extra-time in the quarter-final against Uruguay, and Ghana lost on penalties.
Gyan spent one full season at Sunderland, where he scored ten times, before moving to Emerati team Al-Alin on loan for the 2011-2012 season.