The diet of the barn owl from three localities in Thessaly, Central Greece, was studied in the breeding and non breeding seasons over one year. A total of 420 pellets with 1.013 prey items were analyzed. Twelve small mammalian species were taken (94.9% by number and 96.1% by biomass), although Mus domesticus (26.3%), Crocidura spp. (25.3%) and Apodemus spp. (18.4%) were the main species predated by number. Rats (Rattus spp.), showed the highest frequency (11%) and biomass percentages observed to date in Greece, and their presence in the barn owl diet is also among the highest in the Mediterranean Europe. Birds (Passer spp. and Carduelis spp.) and insects (Acrididae) were also present (3.9% and 1.2%, respectively). Ecological niche values, seasonal and geographical differences were tested, the results pointing to the opportunistic feeding behavior of the barn owl in the croplands of central Greece.