Those employees have been working without a contract. Members of "Unite Here Local 2" authorized a strike last month amid contentious negotiations.
The impacted hotels in San Francisco include: The Courtyard Marriott Downtown, The Marriott Marquis, Marriott Union Square, The Palace Hotel, The St. Regis, The W, And The Westin St. Francis.
Marriott says hotels will still remain open.
It's the first strike for Marriott workers in San Francisco since 2004.
Workers went on strike in Boston earlier this week and are threatening to expand the strike to other cities.