A steam trap cover has a front panel, a back panel, a top panel, and a first and a second end panel joined along edges forming a rectangular enclosure, and a bottom panel joined along one edge, such that the bottom panel may be opened or closed, the first and second end panels each having a circular opening and a slit from a bottom edge of the end panel into the circular opening. The cover is characterized in that with the bottom panel open and the slits in the end panels separated the cover is adapted to be placed over a steam trap having an inlet and an exit pipe until the entrance and the exit pipe are enclosed in the circular openings, after which closing the bottom cover completely encloses the steam trap.