Tuesday's announcement pertains to a store at 1211 Embarcadero. Workers at a store in Pleasanton filed a petition in early March.
Fourteen people work at the Oakland store, and a supermajority are in favor of unionizing, a barista said in a phone interview Tuesday.
The store has been understaffed, barista Nick Ratto said, and while workers got a pay raise recently, managers cut employees' hours.
Ratto added the understaffing has caused stress for workers, who are doing the job of one-and-half to two employees, he said.
Employees, or "partners" as Starbucks calls them, want their store to be an "enjoyable place to work" and they want to earn more money, Ratto said.
Starbucks spokesperson Andrew Trull said in an email Tuesday, "We believe our direct relationship as partners is core to the culture and experiences we create in our stores. We recognize that a subset of partners feel differently--and we respect their right to organize and to engage in lawful union activities."
Fewer than three percent of U.S. company-owned stores have chosen to petition for union representation, according to Starbucks.
Eighteen Starbucks stores in California so far have unionized. That includes stores in Berkeley, two in Santa Cruz and one in Capitola.