While banding Cactus Ferruginous Pygmy-Owls (Glaucidium brasilianum cactorum) in Arizona, we removed three Protocalliphora sialia (Diptera: Calliphoridae) from the wing margin of one nestling. Subsequent inspection of nest material revealed an additional 119 Hesperocimex sonorensis (Hemiptera: Cimicidae), another hematophagous parasite. All nestlings (n = 3) fledged successfully, but on day 8 postfledging, two fledglings were found dead and one was missing. Although unsubstantiated, the subclinical effect (e.g., anemia) of these hematophagous parasites may have contributed to the fledglings' demise. This is the first published record of P. sialia parasitizing Ferruginous Pygmy-Owls and the first documented infestation of H. sonorensis for nesting Ferruginous Pygmy-Owls.