He made his debut in the professional football squad of
FC Zwolle in the 2004–05 season. He also played for
FC Eindhoven before joining RKC Waalwijk. In 2007 Janssen was called up by
Jong Oranje coach
Foppe de Haan to be part of his squad for the
2007 UEFA European Under-21 Football Championship where they qualified for the
2008 Summer Olympics. He scored his first and only goal for Jong Oranje to ensure that they won their final warm-up match against Poland before the competition. At the 2007 UEFA European Under-21 Championship, Janssen came on as a substitute and scored both penalties he took during the series (1–1, 13–12 after 32 penalty kicks) in the semi-finals against
England. The Dutch went on to retain their 2006 title by beating
Serbia 4–1 in the final. In 2017, Janssen played for
RKSV Nuenen. ==Personal life==