Lyme borreliosis is a vector-borne zoonotic disease transmitted by ticks infected with spirochetal bacteria belonging to the genus Borrelia. Affected dogs typically develop intermittent lameness, fever, inappetance, lethargy, and locoregional lymphadenopathy. Although infrequently reported, clinical manifestations in horses include neurological abnormalities, uveitis, nuchal bursitis, and cutaneous pseudolymphoma. Diagnosis is based on a combination of history, clinical signs, laboratory findings, exclusion of other diseases, and response to treatment. Treatment consists of an extended (eg, 30-day) course of antimicrobials, supportive measures including analgesia, and immunosuppressive therapy in the case of immune-mediated reaction.