Chicago (10-16) won its second straight as it erased a 10-point fourth-quarter deficit with a 28-13 effort in the final 10 minutes.
Stefanie Dolson scored 18 points, Allie Quigley had 15 and Cappie Pondexter added 12 for the Sky, who finished with three wins in four meetings with the Dream this season.
Quigley forced an 80-80 tie on a running layup and Chicago went ahead for good at 82-80 on a pair of Dolson free throws with 2:54 left in regulation.
Brittney Sykes and Tiffany Hayes each scored 13 points for Atlanta (10-15) while Elizabeth Williams added 11 points and 12 rebounds as the Dream dropped their fourth straight.
Atlanta led 48-40 with 1:45 left in the opening half before the Sky rallied to trim the halftime deficit to three behind Vandersloot's 3 pointer and Pondexter's jumper and two free throws.
The Dream reestablished control in the third quarter, outscoring the Sky 23-16 to open a 73-63 lead entering the final 10 minutes.