Lindsay Whalen missed a game-tying jumper at the buzzer, sending Connecticut (5-6) to its second straight loss and third in four games.
Detroit (3-7) has beaten Connecticut in 10 of the past 13 matchups.
"Katie Smith makes tough shots," said Connecticut forward Asjha Jones, who was guarding Smith when she made the game winner.
"Asjha came out and I put the ball on the floor," Smith said. "Fortunately, I was able to knock it down."
Connecticut led 77-76 with 55.9 seconds left in overtime. Kara Braxton made a free throw to tie it.
Jones led Connecticut with 23 points and 10 rebounds. Whalen had 20 and Kerri Gardin had 12.
Tan White made two free throws with two seconds left in regulation to tie the game at 67.
The Sun led 63-58 in the fourth period, but didn't make a field goal for the final 5:27. The Sun missed 10 straight shots.
"I don't have an answer for this one," Connecticut coach Mike Thibault said. "Right now, our offense is so scattered."
Detroit was whistled for four technical fouls, three in the fourth quarter.
"When you see the coaches care that much and you know they've got your back, you want to do your part," Smith said.
Detroit's bench outscored Connecticut's 36-9.
Connecticut played without forward Tamika Whitmore, who missed the game with a calf injury. It ended Whitmore's streak of 204 straight games played, the longest active streak in the WNBA. Detroit guard Deanna Nolan, its leading scorer, missed the game with a hamstring injury.
Source: AP News