Playing career 
Järvenpää played for Kärpät in Finland's top-flight Liiga in the early- and mid-1980s. From 1986 to 1989, he played 114 games for the Winnipeg Jets in the National Hockey League (NHL). He then returned to Finland and joined Lukko in 1989, where he spent two years. The 1991–92 season saw him skate for Leksands IF in Sweden. After wearing Jokerit colours in 1992–93, he moved to fellow Liiga team Espoo Blues, where he spent the last two years of his playing career. Järvenpää represented Finland's national team on several occasions, including the 1992 Olympic Games and the World Championships in 1985, 1986, 1989, 1991 and 1992 (silver medal). Coaching career 
He served as assistant coach of Liiga team SaiPa from 2003 to 2005 followed by a one-year stint with fellow Liiga outfit Lahti Pelicans in the same position. Järvenpää took over head coaching duties at HDD Olimpija Ljubljana, a Slovenian member of the Austrian Hockey League (EBEL), in 2009 and remained in that job until 2012. He then served as head coach of fellow EBEL team EV VSV from 2012 to November 2015, when he was sacked. In early January 2016, he was named head coach of Alba Volán Székesfehérvár and parted ways with the EBEL team at the end of the 2015–16 season.
Playing career 
Järvenpää played for Kärpät in Finland's top-flight Liiga in the early- and mid-1980s. From 1986 to 1989, they played 114 games for the Winnipeg Jets in the National Hockey League (NHL). They then returned to Finland and joined Lukko in 1989, where they spent two years. The 1991–92 season saw them skate for Leksands IF in Sweden. After wearing Jokerit colours in 1992–93, they moved to fellow Liiga team Espoo Blues, where they spent the last two years of their playing career. Järvenpää represented Finland's national team on several occasions, including the 1992 Olympic Games and the World Championships in 1985, 1986, 1989, 1991 and 1992 (silver medal). Coaching career 
They served as assistant coach of Liiga team SaiPa from 2003 to 2005 followed by a one-year stint with fellow Liiga outfit Lahti Pelicans in the same position. Järvenpää took over head coaching duties at HDD Olimpija Ljubljana, a Slovenian member of the Austrian Hockey League (EBEL), in 2009 and remained in that job until 2012. They then served as head coach of fellow EBEL team EV VSV from 2012 to November 2015, when they were sacked. In early January 2016, they were named head coach of Alba Volán Székesfehérvár and parted ways with the EBEL team at the end of the 2015–16 season.