Barona Resort and Casino security guards alerted San Diego County Sheriff's Department (SDSO) deputies to an international counterfeiting operation.
Deputies arrested Lien Do, Hao Nguyen, and Ben Ven Pham on Christmas Day last year.
They found $300,000 worth of counterfeit chips in the suspects' car.
"It appears that what they were seeking to do was convert those chips into cash and to walk out the casino with the cash," said Prosecutor Daniel Shim.
The defendants were charged with multiple felonies, including grand theft, burglary, forgery and possession of counterfeit marks.
"When the sheriff's department searched their home in Garden Grove, they found about $2 million in casino labels," Shim said. "During Mr. Pham's interview, he indicated he received those chips from Vietnam."
Two of the defendants plead guilty to lesser charges and are serving one-year jail terms. Charges against a third defendant were dropped and he returned to Vietnam.
"The Sheriff's department did a great job in investigating this case. They did a very thorough investigation," Shim said.
The criminal investigation expanded to at least six other casinos in Southern California, several of which are located in San Diego.
It remains unclear if any of the fake chips were actually used in any of those casinos.
"It is still unknown if the operation had any ties to organized crimes," Shim said.