Tom Wandell had a goal and an assist and Brad Richards also scored for the Stars, who got 24 saves from Marty Turco in winning for the second time in three preseason games.
David Backes scored a short-handed goal for the Blues, who also got a goal from Keith Tkachuk.
The Blues fell for the first time this preseason after scoring nine times in two previous victories. Chris Mason stopped 25 shots.
Benn sealed the win for the Stars when he stole a puck from former Star Darryl Sydor and beat Mason to give Dallas a 3-1 lead before Tkachuk scored with 6:19 to play.
Sydor, a 17-year veteran, spent parts of 10 seasons with the Stars. He is in camp with the Blues.
|Loui Eriksson (1) Backhand shot - ASST: Brad Richards (1)|
2 - 1 DAL
|SHG - David Backes (1) Backhand shot - ASST: Steve Wagner (1)|
2 - 1 DAL
|Keith Tkachuk (1) Slapshot - ASST: Alexander Steen (1), David Perron (1)|
3 - 2 DAL
|Jamie Benn (1) Wrist shot - ASST: Tom Wandell (1), Steve Ott (1)|
4 - 2 DAL