The three-vehicle crash involving a car, a camper van and a motorbike happened on near Ralia, some 40 miles south of Inverness, at around 2.45pm today.
Police said the full extent of the injuries is not yet known and those involved have been taken to hospital.
The road has been closed in both directions and a diversion put in place as officers investigate the scene of the crash.
The road, which is the main route between the Highlands and the Central Belt, is notorious for accidents. Last month a crash involving two cars killed three people, including a woman and her young daughter, on the road near Kingussie.
Plans to install average speed cameras along the road by next summer, at a cost of £2.5 million, have since been announced by the government.
There are further plans to make the A9 a dual carriageway over 80 miles by 2025 but campaigners have called for work to be completed sooner.
Police have appealed for any witnesses to the three-vehicle crash to contact them on 101.