We studied the diet of the Acorn Woodpeckers (Melanerpes formicivorus) at La Primavera Forest, Jalisco, Mexico. This resident species had a diverse diet throughout all seasons. The diet included acorns of Quercus viminea, Q. castanea, and Q. laeta, which were stored primarily in granaries in live trunks of pine (Pinus spp.) trees. They also consumed acorns of Q. magnoliifolia and Q. resinosa by piercing and eating just the central part of the seed. Acorn Woodpeckers did not use acorns from species of oak in the same proportion as available. They also fed seasonally on insects (Coleoptera and Lepidoptera) and tree sap.