The collision happened on the A6094 between Wallyford and Dalkeith at about 14:40 on Monday.
The grey Lamborghini Gallardo had been travelling southbound on the A1 and exited at the Wallyford junction before going on the A6094 towards Whitecraig.
A maroon-coloured Ford Focus and a green Ford Fiesta were going in the opposite direction when it happened.
Three men and two women were taken by ambulance to the Royal Infirmary of Edinburgh for treatment.
The road was closed while police investigated the scene and officers are appealing for witnesses.
PC Julie Bishop, of Police Scotland, said: "Our inquiries into this matter are ongoing and I would be interested to hear from anyone who saw these vehicles prior to the collision to contact police.
"Likewise, I would ask anyone who saw the collision itself to come forward if they have not already done so."
Five people have been treated in hospital after a three-car crash in East Lothian involving a Lamborghini.