Ten of the 40-inch-square portraits feature famous athletes of the 1970s, including boxer /*Muhammad Ali*/, golfer Jack Nicklaus, soccer star Pele and figure skater Dorothy Hamill. The other is of Weisman.
A $1 million reward is being offered for information that leads to the stolen paintings.
"In my opinion it's one of the most expensive, significant art thefts in the history of Los Angeles, said Richard Rice, an art consultant at Galerie Michael in Beverly Hills.
The original prints were on display in Weisman's dining room and his house was locked up.
The housekeeper noticed the prints missing and called the police.
"This is very unusual, I mean, this is one of the highest value burglaries of art that we've had in the city, in my memory," said LAPD Det. Don Hrycyk.
Police say there was no sign of forced entry and nothing else was taken from the home.
"There was one neighbor that thought maybe they, she had seen maybe a maroon van that may have been parked in the driveway. And that may or may not have something to do with the case," said Hrycyk.
Weisman and /*Warhol*/ were friends, and he commissioned the artist to create portraits of sports figures, including Chris Evert, Kareem Abdul Jabbar, OJ Simpson, Tom Seaver, Willie Shoemaker, Rod Gilbert, Nicklaus, Pele, Hamill, and Ali.
"The theft of Warhol's 'Athlete Series' represents a profoundly personal loss to me and my family," Weisman said in a statement. Weisman, who published a book about his art collection called, "From Picasso to Pop," declined to comment further, saying he did not want to interfere with the investigation.
Art experts say they're one of a kind paintings and truly priceless. Another Warhol painting similar to the one of Ali recently sold for $9 million. Something this unusual can't be put on the market.
"Perhaps stolen to order, where someone would hire a theft to go in and steal a collection like this so they could keep it all to themselves for the rest of their life. It's a possibility," said Rice.
The $1 million reward is being offered by an anonymous donor. Many worry that unless they are recovered quickly, the paintings may never be seen again.
Hrycyk said the weeklong delay in announcing the theft was to allow detectives to confirm the reward and gather descriptions and photographs of the missing artworks.
The Associated Press contributed to this report.