Nottinghamshire Police said the road is "expected to be delayed for some time".
Officers and paramedics are currently on the scene which has left a section of the A57 between the A1 junction and the Manton Wood Roundabout.
Police were called to reports of a collision just before 10.45am today.
The incident involved a car and a motorbike.
A police spokesman said: "A man has been injured and the extent of his injuries are not yet known."
If you saw what happened, call Nottinghamshire Police on 101, quoting incident number 204 of 15 August 2019.