Tocchet, 38, joins the staff of Coach Tony Granato that already includes Jacques Cloutier and Paul Jerrard.
"Rick played at the highest level of hockey in the world for 18 seasons and brings with him a vast amount of qualifications and hockey knowledge," said Granato, who was an assistant for just 2 1/2 months before he was promoted last month.
"Rick was a gifted offensive player who played the game with a high degree of grit, determination and a great work ethic, which are qualities we as a coaching staff want to focus upon on a daily basis."
Tocchet accumulated 440 goals, 512 assists and 2,972 penalty minutes in 1,144 games with Philadelphia, Pittsburgh, Los Angeles, Boston, Washington and Phoenix.
"The Avalanche organization has an exceptional track record, and the challenge of continuing this tradition is something very appealing to me," he said. "I know many of the players on the team and I'm looking forward to working with them."