The vehicles involved were a red Renault Megane and a silver Ford B Max and a Scottish Citylink coach, carrying 16 passengers.
Police Scotland said four people were taken to Aberdeen Royal Infirmary.
Officers said the male coach driver suffered minor injuries.
None of the passengers on the coach were injured.
Road Policing Chief Inspector Stewart Mackie said: “This has been a challenging incident for the emergency services to deal with.
“My thoughts are with the families of all those affected by this.
“The road is anticipated to remain closed for some time to allow collision investigation to take place.
“This is likely to be a complex enquiry that will take some time.
“I am grateful to the public for their patience while this is carried out.
“Further details will follow once they are available.
“I would ask that anyone who witnessed the incident and who hasn’t already spoken to the police contacts officers on 101 using reference number 2576 of 12 March.”
Traffic was diverted via the A92.
A Scottish Citylink spokesperson said: “One of our coaches travelling from Glasgow to Aberdeen was involved in a serious multi-vehicle accident this afternoon on the A90 near Glenbervie Junction.
“Our immediate thoughts are for those involved in the incident.
“Safety is our absolute priority and we will assist police with their inquiries into the circumstances.
“There were no reported injuries to passengers travelling on the coach and they were provided with alternative transport to take them to Aberdeen bus station.”
The crash brings to seven the number of people killed on Scotland’s roads over the last nine days.
An 89-year-old woman who was a passenger in a car which collided with two other cars in Aberdeen last Thursday died on Sunday.
On the same day, a 56-year-old man died after being hit by a car in Kirkcaldy a week before.
A 69-year-old woman died after her car collided with five stationary vehicles in Lenzie on Saturday.
A 57-year-old female cyclist died when she collided with a car on the B9152 near Loch Alvie between Aviemore and Kincraig on Monday, 4 March.