A study was conducted to analyze diet of Cooper’s hawk (Accipiter cooperii) to determine the occurrence of Mearns quail (Cyrtonyx montezumae) in hawk diets in the northwestern region of the State of Mexico and to study some morphological characteristics of Cooper’s. The study area was defined as published in the hunting proclamation 1997 for Region II which encompasses 249,000 ha, 73 % forest land and 27 % grassland. Eighteen Cooper’s hawks were presumably residents according to their morphological characteristics. Nesting activity was observed from February to mid March, while breeding behavior and hatching were from March to May. Territory was defended in a surrounding area of 4.5 km2. Four nests were found within forest land areas (38 to 50 % of the habitat). Four hawk pellets were collected and analyzed, showing prey differences between pellets. Mearns quail was found in only one of the four pellets analyzed. Cooper´s diet was based on several small birds: Zenaida macrorura, Sturnella neglecta, Piranga ludiviciana, Toxoma ocellatum, Toxoma curvirostre, Turdus rufopalliatus, Scardafella inca, Colombina passerina, Zenaida asiática, Aechmolophus mexicanus, Mimus ployglottos and Cyrtonyx montezumae. This study suggests that there is a small Cooper’s hawk resident population in the region, and that Mearns quail in not the main prey as suggested previously.