A system for detecting leaks in a sealed insulating glass unit (IGU) includes a pressure source, a flow path that extends between the pressure source and a distal end removably coupleable to the IGU to place the pressure source in fluid communication with an interior space of the IGU, and a pressure sensor to monitor a pressure level in the interior space. A method for testing the IGU for leaks includes applying a pressure to an interior space of the sealed IGU, monitoring the pressure in the interior space, and determining whether one or more failure conditions exists by comparing the monitored pressure to a desired pressure after a specified period of time. The IGU failure exists if the monitored pressure is less than the desired pressure (e.g., less than the desired pressure by more than a predetermined amount) after a first specified period of time, if after reaching the desired pressure the difference between the applied pressure and the desired pressure is greater than a predetermined amount after a second specified period of time, or if one or more of the glass lites breaks.