The Sun improved to 12-8 after rallying from a five-point halftime deficit with a 33-10 third quarter. That allowed them to cruise to their 12th win in the last 16 games after an 0-4 start.
Connecticut, the surprising Eastern Conference leader after being expected to go through a rebuilding season, is 11-3 after opening 1-5.
Trailing 44-39, the Sun ran off 14 straight points in the third quarter to take control of the game with a 10-point lead. The margin ballooned to 18 when Shekinna Stricklen hit a 3-pointer with 35.6 seconds remaining in the third quarter.
Alyssa Thomas, Jonquel Jones and Jasmine Thomas all posted 13 points apiece. Alyssa Thomas grabbed nine rebounds and Jones, the league's leading rebounder, grabbed six and also blocked two shots. Alex Bentley had seven assists in the win.
The Stars (2-17) failed for the third time this season at a two-game winning streak, falling to the Sun for the third time this season.
Isabelle Harrison led San Antonio with 17 points and six rebounds. Kayla McBride scored 14 points, Kelsey Plum had 11 and Dearica Hamby came off the bench to add eight points and 10 rebounds.
San Antonio, which trailed by seven at the end of the first quarter, held the home team to 14 second-quarter points to take the 40-35 halftime lead.
The Stars wrap up their two-game road trip when they visit the Atlanta Dream on Tuesday night. The Sun host the New York Liberty in an 11 a.m. ET Wednesday game at the Mohegan Sun Arena.