It was Stewart's first game in Seattle since going to the Liberty as a free agent during the offseason. The former MVP helped Seattle win two titles with Sue Bird, who sat courtside for the return.
Stewart is the second player in WNBA history with at least 25 points and 10 rebounds in her first game against a former team, joining Chamique Holdsclaw, who had 27 points and 10 rebounds in 2005 against the Mystics.
Stewart took over in the third quarter with 10 points and six rebounds to help New York extend a narrow halftime lead to 68-56 entering the fourth. She finished 8-of-14 from the field and 8-of-9 at the stripe.
Seattle got within single digits early in the fourth before Sabrina Ionescu sank a deep 3-pointer to make it 72-61. Stewart's fast-break layup, off a nice pass from Courtney Vandersloot, gave New York an 86-74 lead.
Ionescu finished with 20 points for New York (3-1), which has won three straight games. Stefanie Dolson scored 10 points and Vandersloot had a season-high 11 assists. Jonquel Jones scored nine points in 18 minutes.
Kia Nurse made Seattle's first 3-pointer of the game with 4:15 left in the third quarter to get within 57-53, but New York made 3-pointers on its next two possessions and Stewart followed with a three-point play for a 13-point lead.
The Associated Press contributed to this report.