On March 9, 2006, he was traded to the Ottawa Senators for Brandon Bochenski and a second-round pick. He played 19 games with the Senators and became an unrestricted free agent. On July 1, 2006, he signed a one-year deal with the Colorado Avalanche. He played 2 seasons with them and signed a one-year two-way contract with the New York Rangers for the 2009–10 season on July 3, 2009 but he never played for them. Arnason retired from playing professional ice hockey in 2012.