A group marched to North Park and attended a post-march rally in Balboa Park.
"This is a civil rights movement. What we want is equality for all," said Marty Theis.
The "equal rights" march attracted a crowd estimated at 8,000 to 10,000, according to the San Diego Police Department. Participants began their march around noon from Third and University in Hillcrest. The group marched to North Park and then attended a post-march rally in Balboa Park.
"I am so proud to be a part of this in San Diego, said Jennifer Schumaker, a self-proclaimed 'lesbian soccer mom'.
"I think Prop. 8 is our Rosa Parks and I think there is no way that gay people and their friends or families are going to sit down for discrimination again," said Schumaker.
Police said there were no arrests and no problems.
San Diego is one of several cities up and down the state to hold marches in recent days to protest Tuesday's passage of the measure, which bans same-sex marriage in California. Two-thousand people opposed to the ban on gay marriage took to the streets of Long Beach Friday and three were arrested. In San Francisco, 1,000 people hit the street, shutting down Market Street.
The ACLU has filed a petition with the California Supreme Court to overturn Proposition 8, with the ACLU saying the measure never should have been on the ballot in the first place.
"I mean the constitution says you can vote on a lot of things. But there are a lot of things you can't put up to a popular vote because that's a constitutional right," said David Blair-Loy of the ACLU.
He also said that legal groups tried to keep the issue off the ballot, but that the California Supreme court said, "We're not going to hear that right now."
But conservative activists say they want to apply the same formula they used to outlaw same-sex marriage in California to prevent other states from recognizing gay unions and President-elect Barack Obama from expanding the rights of gays and lesbians.
Leaders of the successful Proposition 8 campaign say an unusual coalition of evangelical Christians, Mormons and Roman Catholics built a majority at the polls Tuesday by harnessing the organizational muscle of churches to a mainstream message about what school children might be taught about gay relationships if the ban failed.