Nanocomposite gears and standard mechanical testing specimens based on polyoxymethylene containing different fractions (0, 3, 6, and 9 wt%) of nanosized precipitated calcium carbonate particles were produced by using twin-screw extruder and injection molding machine. The wear and temperature of gears teeth were measured by a gear test rig. The morphologies of fractured gears teeth were analyzed by using scanning electron microscopy. Results of experiments indicate that the incorporation of CaCO3 nanoparticles into polyoxymethylene increases the flexural and heat resistance and reduces the magnitudes of wear and temperature of gears noticeably. The maximum flexural resistance is achieved by employing 3 wt% of CaCO3 nanoparticles. Gears containing 3 wt% of CaCO3 nanoparticles present the lowest wear rate, which is 61% smaller than that of neat polyoxymethylene gear. The life time (durability till failure) of nanocomposite gear was twofold as compared to neat polyoxymethylene gear. The nanocomposite gear showed abrasive-wear and brittle-fracture, yet the neat polyoxymethylene gear demonstrated prevailing cohesive wear and ductile failure.