A 17-month-old girl and a 50-year-old man died when the car they were in collided with another car and then hit a tree.
Lancashire Police said the white Land Rover Discovery the pair had been in crashed with a Mini Cooper and then a tree in Tarleton at about 08:25 GMT.
The girl and man died at the scene of the crash in Hesketh Lane, near the junction with Oaklands Avenue.
The driver of the Mini was taken to hospital with minor injuries.
Police urged any witnesses or anyone with dashcam footage to contact them.
Sgt Matt Davidson, of Lancashire Constabulary's serious collision investigation unit, said: "These are terribly sad and tragic circumstances that have resulted in a man and a young girl losing their lives this morning.
"Our thoughts are very much with their loved ones at this awful time."