Wild and domestic animal cohabitation may result in parasite cross-transmission. Our objective was to identify the presence and seasonal shedding of gastrointestinal parasites in mule deer (Odocoileus hemionus) and cattle (Bos taurus) on the Mapimí Biosphere Reserve, Durango, Mexico. We collected 66 cattle and 222 mule deer fecal samples and analyzed them with McMaster flotation, fecal culture, and Baermann techniques. We identified parasite genera Eimeria, Haemonchus, Bunostonum, Cooperia, and Trichostrongylus in cattle; and Eimeria in mule deer. No common parasites were identified between the two species. Fecal parasite counts increased during periods of higher precipitation and temperature.