Happy Birthday, Jessica Lowndes!

90210 star Jessica Lowndes celebrates her 20th birthday with a Baskin Robbins cake on Saturday in Beverly Hills, Calif.

The actress, who plays troubled Adrianna Duncan on the hit CW show, got down at the Tava masked party at Bond Street in the upscale district. Costar Tristan Wilds was there to celebrate the big day. HAPPY BIRTHDAY, JESSICA!

One more pic below of Jessica shooting a scene with Jennie Garth and Shannen Doherty at the Gay and Lesbian Center in Hollywood earlier in the week.

A new episode of 90210 airs tomorrow, Nov. 11 @ 8PM ET/PT on The CW.