The Blues are waiving the veteran forward for the purpose of buying out his contract, the team announced on Tuesday.
Drouin played just nine games for the Blues after joining the team in a March trade that sent captain Brayden Schenn to the New York Islanders.
The 31-year-old posted one goal and two assists for the Western Conference club after tallying three goals and 18 assists in 55 games on Long Island.
Drouin, of Sainte-Agathe, Que., has played 671 NHL games since he was the third-overall pick in the 2013 draft, registering 111 goals and 287 assists.
He had one season left on his contract at $4 million.
The buyout window for all teams closes at 5 p.m. on Tuesday.