A pneumatic can crusher for compressing a metal can has a hollow pipe. A piston assembly is located inside the pipe with a head attached to a first end of a connecting rod and a bottom air cylinder connected to a second end of a connecting rod. In some embodiments, an opening is located in the pipe near the top end, for allowing the metal can to be inserted into the inside of the pipe and placed on a top surface of the head of the piston assembly. The pneumatic can crusher has a manually activated safety interlock operated by a foot of a user. Air from the air compressor pushes the air cylinder upward toward the top end of the pipe so to crush the metal can on the top surface of the head of the piston assembly.