Tina Charles totaled 20 points and a game- high 13 rebounds as Connecticut downed Washington, 77-70.
Kara Lawson totaled 16 points, Mistie Mims had 15 with seven boards and Renee Montgomery added 11 points off the bench for the Sun, the Eastern Conference leaders.
Crystal Langhorne poured in a game-best 23 points, while both Noelle Quinn and Shannon Bobbitt scored 10 points for the Mystics, who have lost six in a row and sport the league's worst record at 5-22.
Charles hit a layup just before the midway point of the third quarter and the Sun led 57-44.
But the hosts continued to chip away, eventually taking a 67-66 lead with 4:22 remaining on a Matee Ajavon jumper.
Montgomery followed with a trey and Charles added a hook shot for a 71-67 game with 2:53 to play, and Washington only got as close as 71-70 on a Bobbitt runner with 60 seconds left.
Charles hit a layup then four free throws down the stretch salted away the victory.