Riihilahti started his career at HJK where he made his Veikkausliiga debut in 1995. He has won the Finnish championship four times (1997, 2009, 2010 and 2011), the Finnish Cup three times with HJK, and the Finnish League Cup three times, and played a vital part when the first and so far only time Finnish Club team qualified for the UEFA Champions League in the 1998–99 season. After first spell in HJK, Riihilahti then moved to Norway's Vålerenga I.F. for the 1999 season.