Helmer went undrafted but was signed as a free agent by the New Jersey Devils in 1994. He never played a game with the Devils, instead playing with their minor league affiliate Albany River Rats for 5 years. His most successful season with the River Rats was during the 1997–98 season when he scored 63 points in 80 games along with 101 PIM and an appearance in the AHL All-Star Game. Following the 1997–98 season Helmer signed with the Phoenix Coyotes. He made his NHL debut with the Coyotes, appearing in 11 games. He was then released and later claimed on waivers by the St. Louis Blues. He appeared in another 29 games with the Blues, notching four assists. The 1999–2000 season saw Helmer play the majority of the year with the Worcester IceCats while also appearing in 15 games with the Blues. On February 12, 2000, Helmer scored his first career NHL goal against Guy Hebert and the Mighty Ducks of Anaheim in a 6-3 Blues victory After the 1999–2000 season, Helmer signed with the Vancouver Canucks. He spent the next three years bouncing between the Canucks and the minors. The 2001–02 season saw Helmer achieve NHL career highs with ten points and 53 PIM. In addition, Helmer played six games in the playoffs that year, the only time he has played in the Stanley Cup Playoffs. On July 25, 2003, Helmer was traded by the Canucks back to the Phoenix Coyotes for Martin Grenier. He missed the majority of the 2003–04 season due to a shoulder injury but managed to appear in 17 games with the Coyotes. Prior to the 2008–09 season, this had been the last time Helmer played in the NHL. He signed with the Detroit Red Wings in 2004 but played two years in the AHL with the Grand Rapids Griffins. He was re-signed by the Coyotes in 2006 and had been playing with the San Antonio Rampage. Helmer signed with the Hershey Bears on July 24, 2008, and served as captain of the team. On November 28, 2008, the Washington Capitals signed and recalled Helmer from Hershey due to several key injuries among the Capitals' defensemen. Helmer led the Bears to Calder Cups in 2009 and 2010. While with the Oklahoma City Barons, Helmer became the AHL all-time leading scorer among defencemen in 2011, passing John Slaney. Helmer has 562 points in 1093 AHL games. After captaining the Barons in his second season with the club, Helmer was left unsigned through the beginning of the 2012–13 season, due to the NHL lockout. After an agreement was reached, Helmer was signed by the Springfield Falcons on January 9, 2013. In 2017, he was inducted into the AHL Hall of Fame.
