Martinson's first head coaching job was with the
San Diego Gulls of the
West Coast Hockey League in 1995. Martinson was hired as the team's first head coach after playing for the
former Gulls team that played in the IHL. He had immediate success in the newly formed league and the WCHL Gulls won the first three league championships, the Taylor Cup, in 1996, 1997, and 1998. He coached the Gulls for nine of the team's eleven seasons, winning two more Taylor Cups, in 2001 and 2003. After one season of coaching the Gulls after the team joined the
ECHL in 2003, Martinson left the organization to become the head coach of the
Rockford IceHogs in the
United Hockey League in 2004. He stayed with the IceHogs for three seasons, winning the league championship in 2007. Martinson then left the IceHogs after the championship season to become the head coach of the
Elmira Jackals in their first season in the ECHL in 2007. With the Jackals, his teams qualified for the playoffs every season following multiple years of no postseasons before he was hired. In 2010, Martinson left the Jackals to become the inaugural head coach of the expansion
Chicago Express in the ECHL. However, the Express did not take the ice until 2011 would end up only playing one season in
2011–12. After the Express folded in 2012, Martinson became the head coach of the
Allen Americans in the
Central Hockey League. His teams once again had immediate success winning the 2013 and 2014 Ray Miron President's Cup for the CHL's playoff championships. The Americans joined the ECHL in 2014 and continued to have success, winning the league championship
Kelly Cup after their first two seasons, in
2015 and
2016. Martinson’s contract was not renewed by Allen following the 2021-22 season. Over his multi-stop coaching career Martinson won a total of ten championships in four North American ice hockey leagues, including five with the Gulls (1996, 1997, 1998, 2001, 2003) in the West Coast Hockey League, four with the Americans in the Central Hockey League (2013, 2014) and the ECHL (2015, 2016), along with one with the IceHogs in the United Hockey League (2007). Martinson is the first American-born coach to win 1,000 games as a head coach, having completed the 2021-22 season with 1,123 wins. On June 27, 2024, Martinson was named as head coach of the
Federal Prospects Hockey League expansion team, the
Athens Rock Lobsters, in their inaugural season, leading them to the 2024 FPHL playoffs while winning Coach of the Year award. On May 12, 2025, it was announced that Martinson would rejoin the Americans and take up his old job as head coach and GM. ==Post-coaching career==