As a result, the 76-year-old female driver of the Honda and an 81-year-old male passenger were taken to the Balfour Hospital in Kirkwall for treatment to serious injuries.
The 65-year-old female driver of the Citroen was also taken to hospital and was checked for minor injuries.
Sergeant Angus MacLeod said: “I would urge anyone who may have witnessed the crash or seen either vehicle beforehand to get in touch if you have not already spoken to a police officer.
“We would also be keen to speak to anyone who may have dashcam footage.”
The force are asking anyone with information can call 101, quoting incident 2671 of August 29.
Man, 81, and woman, 76, taken to hospital with ‘serious’ injuries after Orkney crash