The incident happened just after 12:30 p.m. in the area of N. Pennock Avenue and Parkview Road.
Chopper 6 was over the area, which showed a large scene, with police officers investigating along the Cobbs Creek and railroad tracks.
Police say details on how the shooting unfolded are not known at this time.
A message from Delco DA's office stated:
I can confirm that there has been an officer-involved fatal shooting in Upper Darby.
An independent investigation will be conducted by the District Attorney's office, led by Deputy District Attorney Doug Rhoads.