The festivities, which included a fireworks-and-confetti display, were set outside the Sleeping Beauty Castle and began with televised images echoing the fanfare of the park's launch in 1955.
"Dad's vision called for this, for Disneyland, to be something that could grow more beautiful every year, and it has," said Diane Disney Miller, one of founder Walt Disney's two daughters.
Broadcaster Art Linkletter, 93, who hosted the live telecast of the park's opening day along with Ronald Reagan and actor Bob Cummings, also was on hand.
"I'm not only happy to be here, I'm happy to be anywhere," said Linkletter, who also was celebrating his birthday Sunday.
Gov. Arnold Schwarzenegger, who emerged from the castle gates with Mickey Mouse's white-gloved hand on his shoulder, praised the theme park's contributions to the state's economy.
"This is an engine that drives California tourism and our economy," he said. "Thank you for 50 wonderful years."