Los Angeles missed its first seven shots of the fourth quarter until Chelsea Gray's 3-pointer gave the Sparks a 66-62 lead with 5:48 remaining. Parker, back after missing five games, sank a 3-pointer with 2:30 remaining for a 74-68 lead.
Gray added 16 points and 10 assists for Los Angeles (12-8), which has won six of seven. Chiney Ogwumike did not play after getting a tooth pulled.
Las Vegas trailed 24-15 at the end of the first quarter after shooting 30%, but the Aces opened the second on a 12-2 run to take a 27-26 lead.