Just before 7:00 p.m. in the 500 block of Bonnybrook Avenue in Trappe Borough officials say about 20 people were on the deck when it gave way.
The group was reportedly on the deck about to pose for a photo when it collapsed.
Two people were taken to Lehigh Valley Medical Center and two others were taken to Phoenixville Hospital.
None of the injuries are considered life threatening.
Pennsylvania State Police are investigating.