Emergency services were called to the B6403 Ermine Street at Ancaster, just past Church Lane, after the collision was reported at around 5.35pm.
A Lincolnshire Police spokesman said it involved a Ford Focus and an ambulance and occupants suffered minor injuries.
The ambulance contained a driver and passenger but was apparently on a training exercise and had no patients on board.
“A 26-year-old man was arrested for a traffic offence and was later released under investigation. Our investigations continue.”