The discovery was made around 3:45 p.m. on the 1500 block of South Stillman Street.
Police say they were serving a warrant near the vacant home when officers noticed flies on the window of a boarded up home.
The man's body was badly decomposed on the floor, said police. It appears he had been there for several weeks.
The cause of death is unknown at this time.
Anyone with any information is asked to call police at 215-686-TIPS.