Marchers were accompanied by several supervisors as they reached Civic Center.
The San Francisco Board of Supervisors unanimously passed a measure to support the United Farm Workers in a 25 year struggle to unionize workers at Gerawan farming, a fruit producer in the Central Valley.
"The company has used every legal effort that they can to really prolong the implementation of this contract," UFW President Arturo Rodriguez said.
Gerawan farming disputes that claim and released a statement. It accuses the union of waiting 20 years to negotiate a contract and since then workers voted to decertify the UFW.
An administrative law judge will decide on the dispute in the coming months.