Each deal is worth US$2.5 million, plus $300,000 in bonuses.
The 35-year-old Langenbrunner is coming off a disappointing season, totalling nine goals and 23 assists in 70 games with Dallas and New Jersey. In 2009-10, Langenbrunner had 61 points with the Devils.
Offensively his best season was with Dallas in 2005-06 when he scored 76 points in 81 games.
The move comes a day after St. Louis signed 36-year-old unrestricted free agent Scott Nichol to a one-year contract.
"Jason is a veteran forward and a Stanley Cup Champion who will be a valuable addition to our club," said Blues GM Doug Armstrong. "He's a proven leader and we are excited that he has decided to wear the Bluenote."
The Collingwood, Ont., native was originally drafted by Edmonton in the first round of the 1993 draft.