Pitlick, 30, split last season between the Calgary Flames and Montreal Canadiens, producing five points (one goal, four assists) and six penalty minutes in 39 regular-season games overall.
The Minneapolis, Minnesota, native has appeared in eight NHL seasons, including stints with the Edmonton Oilers, Dallas Stars, Philadelphia Flyers, Arizona Coyotes, Calgary and Montreal.
Across 325 regular-season games he has tallied 89 points (48 goals, 41 assists) and 84 penalty minutes.
The 6-foot-2, 200-pound forward was originally drafted by Edmonton in the second round (31st overall) of the 2010 NHL Draft.
Pitlick will join the Blues for training camp, which begins later this month.
