NEW YORK—One of the founders of poker website Absolute Poker pleaded guilty to criminal charges Tuesday after he was accused earlier this year in a crackdown by the U.S. on Internet gambling.

Brent Beckley, a co-founder of Absolute Poker, was charged in April, along with the founders of PokerStars and Full Tilt Poker, of breaking a variety of U.S. laws, including money laundering and illegal-gambling offenses. Those three websites were the largest poker sites operating in the U.S. at the time.

The criminal charges against 11 people, including Mr. Beckley, marked a long-anticipated showdown between federal authorities and the offshore websites over billions of dollars in revenue from American players. The government claims their operations, by serving U.S. residents, violated U.S. law.

"I knew it was illegal to accept credit cards from players to gamble on the Internet," Mr. Beckley said in Manhattan federal court Tuesday.

Mr. Beckley, who prosecutors said served as the director of payment processing for Absolute Poker, said he and others helped disguise the purpose of the payments in order to persuade banks to process them. "I knew it was illegal to deceive the banks in this way," he said.