The 19-year-old was driving a white Vauxhall Corsa when he was in collision with a blue Nissan Qashqai and a blue Subaru at about 1.15 pm on the A701 south of Beattock.
All three vehicles were damaged and five people were taken to Dumfries and Galloway Royal Infirmary by ambulance with a variety of injuries.
The driver of the Corsa was later transferred to Glasgow with a head injury and a damaged right hand.
His male passenger was detained overnight for observations, whilst the two female passengers were released after treatment for minor injuries.
The female driver of the Qashqai, from Edinburgh, was also released after treatment for minor injuries.
The Subaru was being driven by a 39-year-old man from Galston, accompanied by a 43-year-old woman from Galston, and neither required hospital treatment.
Police are still seeking witnesses to this crash and anyone who can help is asked to call constable James Wishart, Police Scotland at Dumfries on 101.