Phoenix (20-13) is the No. 2 seed in the Western Conference and has home-court advantage in its first-round matchup with Tulsa that starts Thursday night. Los Angeles (14-20) is the No. 4 seed and will open the postseason at Minnesota next Friday night.
Brittney Griner scored 16 points, and Candice Dupree added 12 for the Mercury.
Phoenix led 63-61 when Sparks coach Brian Agler drew a technical foul arguing Jennifer Hamson's foul call against Griner. DeWanna Bonner made the technical free throw, and Griner made both free throws to make it 66-61 with 1:22 remaining. The Sparks pulled to 66-63 before Dupree made two free throws and Currie a layup to seal it.
Hamson scored 12 points, and Ana Dabovic had 10 for the Sparks.