A police spokesman said: "The collision involved a dark grey Vauxhall Vectra motor car and a black Ford Fiesta motor car which collided head-on.
"As a result of the collision, the 58-year-old male driver of the Vauxhall Vectra suffered a serious head injury and was conveyed to Aberdeen Royal Infirmary where his injuries were described as life-threatening.
"The 24-year-old male driver of the Fiesta suffered a broken wrist. A further two passengers in the Fiesta suffered minor injuries and were conveyed to Aberdeen Royal Infirmary."
Inquiries are at an early stage and Grampian Police are appealing for anyone who may have witnessed the crash to contact them.