Blues general manager Doug Armstrong said on the team's Twitter account that the former New Jersey Devils all-star goaltender will practise with the team starting Friday.
The Blues are in need of goaltending help after starter Brian Elliott sustained a lower-body injury last night in a game against the Ottawa Senators.
The 42-year-old Brodeur is the NHL's all-time leader in wins (688) and shutouts (124) and won three Stanley Cups with the Devils (1995, 2000 and 2003).
He split time in the Devils' goal with Cory Schneider last season before leaving the team as a free agent in the off-season.
St. Louis is off to a strong start this season with a 14-6-2 record.