The 66-year-old man and his dog, who was travelling in the back of the Mazda car, were involved in a crash with a grey Mercedes on Pleasley Road, towards Aughton, at around 8am on Tuesday.
Both sadly died at the scene.
The driver of the Mercedes, a 57-year-old man, is in hospital with stomach injuries.
South Yorkshire Police want to speak to anyone who was in the Aughton area yesterday who may have witnessed the crash or saw either vehicles prior to the collision.
Officers are keen to hear from anyone who may have dashcam footage or CCTV.
Anyone with information can call police on 101 quoting incident number 138 of March 9.