Arizona State (5-1) forced overtime with a layup as the regulation buzzer sounded. Carolina (5-2) had a chance to put the game away at the free throw line but missed two shots with nine seconds left that would have put the Tar Heels up four points.
A Xylina McDaniel layup with 27 seconds left in the second half gave Carolina a 76-70 advantage. The Sun Devils answered with a three-pointer by Deja Mann to cut the lead to three.
Jessica Washington made 1-of-2 from the line to make it 77-73, but Adrianne Thomas scored with 15 seconds left to make it 77-75.
Diamond DeShields was fouled and went to the line with a chance to ice the victory, but missed both free throws, setting up the tying layup at the end of regulation by the Sun Devils.
Despite the two misses, DeShields was brilliant for most of the game, scoring a season-high 28 points with eight rebounds and five steals.
One stretch in the second half saw DeShields score 10-straight points and 12-of-14 points in leading the Heels to a 58-53 lead.
Carolina's lead grew to eight points on two occasions, the second time with 3:39 to play, but the Tar Heels were unable to hold its lead down the stretch.
In overtime, DeShields gave UNC a 79-77 lead, but that was short lived as Arizona State scored the next nine points and raced out to a double-digit victory. The Sun Devils made 7-of-8 free throws in the extra session after missing 15 shots from the charity stripe in regulation.
Stephanie Mavunga recorded her fourth double-double of the season with 17 points and 12 rebounds, but fouled out in the final minutes of the second half. Her absence in overtime was felt as the Sun Devils out rebounded the Heels, 49-43 for the game.
Thomas led Arizona State with 23 points, going 13-of-20 from the free throw line. The Sun Devils went to the free throw line 49 times, making 33 of their attempts.
The first half saw neither team lead by more than five points. The lead changed hands four times and the score was tied 10 times in the opening 20 minutes.
Arizona State led 7-4 at the 14:54 mark after a bucket from Arnecia Hawkins. That was the largest advantage for the Sun Devils in the first half.
Mavunga scored six of Carolina's first eight points in the opening minutes, while DeShields got going midway through the half with consecutive field goals to tie the game 19-all at the 8:42 mark.
The Tar Heels finally gave themselves some breathing room late in the first half when Allisha Gray converted a three-point play with 1:24 until halftime. DeShields and Coleman added fast-break layups in the final minute to take a 35-31 lead into intermission.
Carolina will play Illinois on Saturday in the final day of the Cancun Challenge at 3:30 p.m., ET.