Authorities believe the man snuck into a crawl space through an access point on the roof of the Albertsons in the 13000 block of Harbor Bouleard just before 8:30 p.m.
They believe he was trying to steal copper wiring, but police say the ceiling tile gave way, and he nearly fell on top of a cashier.
Officers say the burglar was bold to break in to the store while it was still open.
"This was probably the first time I've heard of someone falling through ceiling tiles while the customers were still there," said Otto Escalante of the Garden Grove Police Department.
Police evacuated the building to search for the suspect. Nearly two hours later, they saw the man walking near the meat department.
The man, who police say was on parole, now faces burglary charges.