McCoughtry added six rebounds, four assists and three steals in Atlanta's fifth straight win. The Dream also received 10 points, eight boards and five blocks from Erika de Souza.
Bria Hartley scored 16 points and Emma Meesseman finished with 15 for Washington, which lost 75-67 to the Dream in the nation's capital on Sunday.
The Mystics have dropped five of six overall.
Notable deaths of 2014 [PHOTOS]