It happened on the eastbound lanes of the QEW, east of Dorval Drive, just before 8 p.m.
Ontario Provincial Police Const. Katie Hulme said five people were transported to hospital with minor injuries.
One person was taken into custody for suspected impaired driving, Hulme said.
Several lanes on the highway were closed for investigation, but they have since reopened.
COLLISION: #QEW Toronto bound approaching Trafalgar #Oakville: HOV, left lane and right lane blocked. #OPP, @oakvillefire on scene. ^aw pic.twitter.com/heP0hc6bx8
— OPP GTA Traffic (@OPP_GTATraffic) December 27, 2019