The 50-year-old man broke into the car in central Cologne on Saturday, but had to abandon plans to strip it of valuables and make a quick escape when the central locking activated and he was stuck.
Passers-by called the police shortly before 7pm to say a man was trapped in the Porsche Cayenne.
Emergency services arrived to find the man sitting in the back seat of the SUV, police said in a statement.
“Eyewitnesses reported that the man kicked the vehicle’s door in panic…but without success,” the statement said.
The car's owner showed up just as fire fighters were preparing to break into the car, and unlocked it, freeing the man.
He was arrested and is expected to be charged with attempted theft from a vehicle.