A probe cover assembly for use in covering and protecting the elongated probe of a medical thermometer. The assembly has three laminated layers, including a flat base layer with an aperture sized to slide over the probe, an intermediate stretchable film, and a protective paper layer having radially-aligned perforations aligned with the base layer aperture. In use, the probe cover assembly is placed on the probe by inserting the probe through the base layer aperture, from the assembly's paper layer side, to stretch the plastic film over the probe, with the perforated paper functioning initially to separate the probe from the film and thereby prevent the film from initially sticking to the probe and stretching unevenly. The probe cover assembly is removed from the probe and discarded by sliding the apertured base layer along the probe, with the perforated paper functioning to scrape the stretched film from the probe. The probe cover assembly is extremely compact and convenient to use, yet highly effective in reliably covering the probe and facilitating an accurate, repeatable measurement of a patient's temperature.