The singer marked her annual milestone with a winter inspired bash at her home in California with her close friends and new husband Evan Ross, reported E! online.
"One of Ashlee's best friends threw her a 'Dirty Thirty' Christmas-themed party at Ashlee's place last night. They had real snow brought in. Ashlee wore a coat and played in the snow," a source said.
"They have huge candy canes all over, Christmas trees, colourful lights draped around," it added.
Evan, the son of legendary singer Diana Ross, took to his Instagram account after the party to post a picture of his wife and her friends sitting in the artificial snow, next to a blow up snowman.