Crombeen's wrister from the high slot went over the glove hand of Andrew Raycroft, who replaced starter Kari Lehtonen at the start of the third period.
David Perron, Brad Boyes and T.J. Oshie also scored for St. Louis, which trailed 2-0 in the third period. Oshie tied it at 3 with 6:18 left in regulation.
The Blues outshot Dallas 31-22 and will play their final preseason game Sunday in Chicago.
Matt Niskanen had three assists for the Stars, who finished with three power-play goals. Severin Blindenbacher and Jamie Benn scored in the first, and Adam Burish put Dallas ahead 3-2 in the third.