The Kings made the move Tuesday before Game 3 of their first-round series with the San Jose Sharks.
Fraser has won two Stanley Cup titles with Chicago in 2010 and Los Angeles in 2012. He has 39 games of NHL playoff experience.
Fraser was sent to the minors two months ago after managing just two assists in 33 games for the Kings. He missed five weeks with a broken hand in the AHL, returning to score six points in 10 games with Manchester.
Los Angeles assigned forward Linden Vey to Manchester on Monday.
This is a great day for me. This is something I've been thinking about for a long time. This is a great opportunity that the St. Louis Blues organization, (owner) Tom Stillman and Doug Armstrong are giving me and trusting me in doing...This is going to be a great challenge for me.
— Martin Brodeur, after announcing his retirement as an NHL player and becoming a senior adviser with the Blues on Thursday