Officers are appealing for witnesses after the man tried to steal one car before being warned off and snatching another in the town last night.
Between 6.10pm and 6.20pm, he attempted to take a blue Citroen which on Friargate which was being driven by a woman who had her young son in the front passenger seat.
She beeped her horn to get attention and a man approached to help, causing the offender to run off.
Around ten minutes later, between 6.20pm and 6.30pm, a bronze Peugeot was parked on St Thomas Street near to the Scarborough Tandoori Restaurant.
A 32-year-old local woman was sitting in the front passenger seat when a man got in, pushed her out and drove off.
The car crashed minutes later on James Street and the man ran away.
The woman who was in the front passenger seat of the Peugeot suffered back and hand injuries when she was pushed out of the car, and needed hospital treatment.
Officers attended and searched the area.
A man in his thirties has been arrested in connection with the offences and is being questioned by police.
North Yorkshire Police is are appealing for witnesses come forward - particularly the man who helped the woman because he left the scene before officers could speak with him.
Anyone with information is asked to contact 101, select option one, and ask for Sarah Walkey. People can also email [email protected]
Quote the reference number 12180003842.