We report the first record of Bronzed Cowbird (Molothrus aeneus) parasitism on the Great-tailed Grackle (Quiscalus mexicanus), which represents the 96th known host for this cowbird species. The record is based on a parasitized clutch, collected from Sinaloa, Mexico, in the collection at the Western Foundation of Vertebrate Zoology. The clutch contained four grackle eggs and one Bronzed Cowbird egg. This record is unusual because the Great-tailed Grackle is extremely intolerant of foreign eggs, ejecting them from their nests almost immediately. As the Bronzed Cowbird expands its range and is studied in greater depth, more hosts will undoubtedly be recorded.