He won the 1997 Danish Amateur Stroke Play Championship and turned professional later that year.

Hansen collected his first professional win at the Challenge Tour's 1998 Navision Open Golf Championship in his home country.

In September 2007, he reached the top 50 of the Official World Golf Rankings and became the top-ranked Danish golfer.

On 11 August 2009, Hansen was charged with tax evasion by Danish authorities for allegedly claiming residency of Monaco, while actually living in Denmark.

European Tour playoff record (1–0) Challenge Tour playoff record (1–0) Other playoff record (0–1) CUT = missed the half-way cut "T" = tied "T" indicates a tie for a place QF, R16, R32, R64 = Round in which player lost in match play "T" = Tied Note that the HSBC Champions did not become a WGC event until 2009.