San Diego Superior Court Judge Patricia Cowett said the coffee-makers - "baristas" - were entitled to $86m in back tips, plus interest.
She issued an injunction banning supervisors from sharing future tips.
She said the practice broke a state law barring managers and supervisors from obtaining a share of employee tips.
A Starbucks spokeswoman, Valerie O'Neil, said the company planned to appeal against the ruling, which she described as "fundamentally unfair and beyond all common sense and reason".
The lawsuit was filed in October 2004 by Jou Chou, a former Starbucks barista in La Jolla, California.
In 2006 the suit was granted class action status, allowing it to go forward on behalf of as many as 100,000 former and current baristas in the chain's California stores.