A native of Finland's capital Helsinki, Söderholm played in the HIFK youth system in the early and mid-1990s before taking his game to North America.

After his third season, in which he served as HIFK captain, he took up an offer from Switzerland and embarked on a two-year stint with SC Bern of the National League A (NLA) in 2005.

On 7 April 2015, after a total of 10 seasons with HIFK's men's team, Söderholm left for a second time abroad in his professional career to provide a veteran presence with German club EHC München of the Deutsche Eishockey Liga (DEL), signing a one-year contract.

[2] He won the German championship in his single season with the München team and announced the end of his playing career several weeks later in May 2016.

[4] In June 2016, a couple of weeks after he ended his playing career, Söderholm was named development coach of EHC München of the German top-flight Deutsche Eishockey Liga (DEL).