The crash happened on the A966 Finstown to Evie road near Tingwall Jetty around 4pm on Sunday.
Patrick Allan, 81, from Kirkwall died in Balfour Hospital in Kirkwall on Monday.
The deceased was a passenger of a red Honda Jazz travelling south.
The crash also involved a brown Citroen Berlingo travelling north.
The 76-year-old woman driving the Honda and the 65-year-old driver of the Citroen have been released from hospital.
Sergeant Angus MacLeod said: “Our thoughts are with the family and friends of Mr Allan and our enquiries are continuing into the crash.
“I’d ask anyone who was recording in the area with dash cam to check their systems and provide any relevant footage to us as soon as possible, or any witnesses to the crash who haven’t yet spoken to officers should come forward as soon as possible.”
Those with information are asked to call 101.