Competitive interactions between coyotes ( Canis latrans ) and federally endangered San Joaquin kit foxes ( Vulpes macrotis mutica ) were investigated at the Naval Petroleum Reserves in California (NPRC) during 1984–1995. Coyotes and kit foxes used similar food items, indicating the potential for exploitative competition. Leporids were the primary prey for coyotes in all years, but small rodents were the primary prey for kit foxes in most years, although leporids were primary prey in other years. Coyotes were the main cause of mortality to kit foxes at NPRC, indicating that interference competition may be occurring. Population trends of kit foxes appeared to be strongly influenced by food availability, but competition from coyotes also may have affected population dynamics of kit foxes. Mechanisms employed by kit foxes, such as resource partitioning, greater dietary breadth, and year-round den use, may facilitate coexistence with coyotes. However, use of anthropogenic food sources by coyotes may intensify competitive interactions during periods of low prey availability.