Objective To report the clinical findings, diagnosis, treatment and outcome of equine patients with articular synovial cysts. Study Design Retrospective case series. Animals Horses (n = 16) with articular synovial cysts. Methods Horses diagnosed with articular synovial cysts (1988–2009) at 2 veterinary teaching hospitals were studied. Signalment, history, clinical signs, diagnostic methods and treatment were retrieved and telephone follow-up was obtained. Results Sixteen horses with articular synovial cysts were identified. Lameness was the reason for referral in most (n = 9) horses. Diagnosis was based on a combination of palpation and imaging studies, including radiography, ultrasonography and/or arthrography. Excision of the cyst was performed in 8 horses. Outcome was available for 4 surgically and 2 conservatively treated horses. Lameness resolved in 3 horses treated surgically and the 4th died for unrelated reasons. The 2 conservatively treated horses performed satisfactorily for the rest of their career. Conclusions Equine articular synovial cysts are rare and can be associated with lameness. The cysts had a synovial lining in all horses where it was assessed. Surgical excision may be successful in resolving the lameness and allowing selected horses to return to work.