Chicago — which qualified for the playoffs with its third win in a row — was without WNBA scoring leader Elena Delle Donne, who missed the game with a foot injury.
Atlanta led 91-90 with 1:45 to go but Erika de Souza scored off an offensive rebound, Jessica Breland hit a jumper and Courtney Vandersloot made two free throws to put Chicago up five with 36 seconds left.
Angel McCoughtry made a jumper, was fouled and made the free throw to cut it to two with 30 seconds. After a turnover, Atlanta had several good looks to tie on the next possession, but McCoughtry missed twice and the Sky held on.
Chicago (18-11) led 52-45 at the break.
McCoughtry led Atlanta (12-17) with 33 points. The Dream had won three in a row.