The former New York Mets and Philadelphia Phillies outfielder pleaded not guilty to grand theft auto and drug possession charges.
Prosecutors say Dykstra leased three high-end cars using phony credit and business information.
Authorities also found cocaine, Ecstasy and synthetic human growth hormone at Dykstra's house when they arrested him in April.
Dykstra was charged with 25 counts and faces up to 12 years in prison if convicted.
He remains jailed on $500,000 bail. He's scheduled to appear in court again on July 11.
The Associated Press contributed to this report.