The collision happened at about 3:45 p.m. ET Friday afternoon near Bloomington Road East and Ninth Line.
The female driver of the minivan was taken to Sunnybrook Hospital with serious injuries. The male driver of the dump truck was treated on scene and has since been released.
Police are urging motorists to avoid the area while they investigate.
York Regional Police's investigative unit says witnesses should call 905-773-1221, extension 7704.
There has been no word yet on any charges.