Scrooby Road in Harworth was closed in both directions as a result of the crash shortly before 7am this morning.
One horse died at the scene and a second horse was later euthanised due to the extent of its injuries.
It is believed the horses escaped from a nearby field.
A third horse also escaped but was safely recovered by police officers.
The driver of the car suffered whiplash injuries but was not taken to hospital.
Inspector Alice Bartle, of Nottinghamshire Police, said: “This was a very sad incident and our thoughts are with the owners of the two horses.
“We are treating this as a tragic accident.
However I would ask anyone who witnessed the collision or has dashcam footage to contact police on 101 quoting incident 187 of 30 January 2022.”