It happened just after 6:00 p.m. at 3rd and Duncannon streets.
Police say the dirt bike and the pickup collided; the dirt bike ended up underneath the truck.
One of the two young men on the bike was trapped underneath the truck and had to be freed from the wreckage.
A 19-year-old and 17-year-old were taken to Einstein Medical Center with serious injuries.
Police are investigating.