Chiney Ogwumike, who missed all of last season with an injury, topped Nneka for the first time in six professional meetings. Nneka Ogwumike had 19 points.
Connecticut started the fourth quarter on a 10-0 run - capped by Alyssa Thomas' three-point play - to take a 75-74 lead. Los Angeles had an 86-82 lead with 4:49 remaining but went the next four minutes without a field goal. The Sun made four straight free throws in the final 30 seconds to seal it.
Every starter for Connecticut (2-0) scored in double figures and Jonquel Jones added 17 points off the bench. Thomas had 15 points, nine rebounds and five assists, and Jasmine Thomas scored 13 points with eight assists.
Chelsea Gray scored 21 points, Odyssey Sims added 20 for Los Angeles (2-1), which was without Candace Parker for a third straight game. The Sparks held a 47-46 lead at the break as both teams shot over 55 percent from the floor.