The critical care upgrade will bring all critical care services into one area over two floors.
Operating theatres at the hospital will be refurbished and an additional theatre will be added to bring the total number of theatres to 10.
Ron Coggins, clinical director for surgical and anaesthetics division at Raigmore Hospital, said: “This investment will not only greatly improve the facilities but also provides an opportunity to co-locate wards and ensure that first-class healthcare can be delivered in modern facilities for years to come.”
The original building at Raigmore Hospital, which services the population of the Highlands as well as Moray and the Western Isles for some specialities, was constructed in 1980.
The investment comes over and above the £29m funding NHS Highland has already secured in principle from the Scottish Government for proposed new hospitals in Aviemore and Broadford on Skye, as part of a wider redesign of health and social care services.