Joseph logged an assist in Saturday's 4-3 win over the Hurricanes.
Joseph Elliotte Friedman of Sportsnet a one-year, $950,000 contract with St. Louis on Tuesday.
Joseph did not receive a qualifying offer from Pittsburgh and will become an unrestricted free agent Monday, Elliotte Friedman of Sportsnet reports.
Joseph registered eight points in the Penguins' last 18 games of the season.
Joseph scored a goal on his lone shot in Thursday's 4-1 win over the Capitals.
Joseph recorded an assist in Monday's 5-2 upset of the Rangers.
Joseph logged a pair of assists in Thursday's 6-3 victory over the Sharks.
Joseph (illness) participated in the morning skate Tuesday, but he isn't expected to be in the lineup against Washington, per Michelle Crechiolo of the Penguins' official site.
Joseph (illness) won't play Sunday against the Islanders.
Joseph (illness) won't play Saturday versus the Blues, Seth Rorabaugh of Tribune-Review Sports reports.