It happened around 12:15 p.m. at Fredonia Place off Hollandale Road.
Police say the truck, owned by McCullough Rubbish Removal, was collecting garbage when the worker, 42-year-old Richard Millward from Levittown, fell off the side of the truck.
He was then run over by the truck's rear wheels.
Millward was rushed to Aria Health-Torresdale where he was listed in critical condition with pelvis and leg fractures.
He will then be transported to Jefferson Hospital for possible internal injuries.
The accident remains under investigation. Anyone with information is asked to call police at 215-633-3719.