Hudgens, decked out in a black mini dress with lace cut-out arms, arrived with beau Zac Efron in a chauffeured Audi Q7, and "when she walked in was completely surprised!" says a guest at the party.
Guests including Ashley Tisdale, Selena Gomez, Brittany Snow, and Corbin Bleu greeted her, while DJ Zen Freeman handled the tunes for the night, playing a mix of hip-hop and top 20 hits.
Efron gave a heartfelt speech – wishing Hudgens a very happy birthday and encouraging guests to have a fun night. Partygoers noshed on East signature dishes including the crab cakes and scallops on the half shell while mingling and dancing.
Hudgen's red velvet birthday cake was presented to her about an hour into the party. "She seemed overjoyed and grateful for the whole experience," says the guest.
"Zac and Vanessa were adorable together," says another guest. "They were smiling at each other and laughing and are really sweet to each other. Great couple."