They were searching Saturday for the suspect, whose name was not immediately released.
Police say the man was in the cruiser parked near Hartford Hospital when he apparently slipped his handcuffs around to the front of his body.
Then, he climbed through a small window into the cruiser's front seat and drove away.
Police found the cruiser dumped in Windsor, and were searching late Saturday afternoon for the suspect.
They have not said why he was in custody in Hartford.