The first incident happened around 5 p.m. Friday at the 15th Street Station in Philadelphia.
A woman told police her son, who has developmental disabilities, was robbed of his wallet while being held at gunpoint by three men.
The victim did not suffer any injuries.
The second incident happened six hours later, around 11:45 p.m., outside the 69th Street Terminal in Upper Darby, Delaware County.
A man said he was assaulted and robbed by three suspects who took cash and his skateboard.
The victim was not injured in this case either.
Anyone with information about these incidents should call SEPTA Transit Police at (215) 580-8111.