Predation by coyotes (Canis latrans) has been documented as the main cause of mortality in most populations of swift foxes (Vulpes velox), although reasons for such high predation rates were often unclear. Additionally, coyotes kill but generally do not consume swift foxes, suggesting coyotes kill for reasons other than food. To better understand ecological relationships between these species, we studied dietary overlap of syntopic coyotes and swift foxes in northwestern Texas from 1998 to 2000. Both species consumed the same food items and had similar seasonal changes in diets, although the order of these items differed for each species. Overall, coyotes and swift foxes had high dietary overlap (Ro  =  0.856), although some dietary partitioning was evident based on food size categories. Dietary overlap was least in summer (Ro  =  0.714) and greatest in winter (Ro  =  0.859). Swift fox diets were dominated by small food items (i.e., rodents and insects), whereas coyote diets had nearly equal representation of all food classes. The similarity in diets between coyotes and swift foxes indicated the potential for resource competition between these species, although we did not determine food availability. Regardless, the killing and spatial displacement of swift foxes by coyotes throughout their distribution might be due to their high food resource overlap, especially because coyote populations tend to be limited by prey availability.