A 9 yr old rat terrier presented with corneal ulceration and conjunctivitis that developed acutely after digging among dry leaves in wooded northern Arizona. Ophthalmic examination revealed multiple linear foreign bodies throughout the adnexal tissue and cornea of the left eye. Manual removal of material was unsuccessful. The palpebral conjunctiva required excision with tenotomy scissors to remove structures and allow corneal healing. Microscopic examination revealed structures believed to be setae from a Theraphosidae tarantula. This was confirmed morphologically by an entomologist and by comparison with hairs from a captive spider of the suspected species. The excised tissue also contained fruiting bodies, hyphae, and microconidia consistent with Aspergillus spp. The captive spider hairs also cultured positive for Aspergillus, suggesting a relationship between this fungus and tarantulas in captivity and in their native habitat. This is the first report in the veterinary literature to confirm tarantula hair as the causative agent in keratoconjunctivitis and corneal ulceration, adding it to the list of differential diagnoses for ocular foreign body. This is also the first report to suggest a relationship between Aspergillus and tarantulas of the Theraphosidae family, which should be considered in the diagnostics and treatment of patients with suspected tarantula hair keratoconjunctivitis.