Objective To report the diagnostic features and clinical outcome of horses with digital flexor tendon sheath (DFTS) synoviocoeles treated tenoscopically under ultrasonographic guidance. Study design Retrospective case series. Animals Client‐owned horses (n = 10). Methods Medical records were searched for horses with lameness localized to the region of the DFTS and clinical evidence of a fluid‐filled mass (synoviocoele) associated with the DFTS. Diagnostic imaging and surgical findings, together with long‐term outcome, were reported. Results Lameness and synoviocoeles were unilateral (5 forelimbs, 5 hindlimbs; 3 lateral and 2 medial in both) and located proximal to the palmar/plantar annular ligament. Synoviocoeles had a firm consistency and focal pain with inability to deflate on non–weight‐bearing examination. Intrathecal DFTS anesthesia was positive in 7/8 horses in which it was performed, with the remainder localized to the region of the synoviocoele using perineural and/or intralesional anesthesia. Communication between the DFTS and synoviocoele was suspected ultrasonographically in all cases and confirmed on contrast tenography (6/6). Tenoscopic fenestration of the communication between the DFTS and synoviocoele under ultrasonographic guidance, with treatment of concurrent intrathecal injury (4/10), resolved the lameness in all horses re‐evaluated by a veterinarian (9/9) and allowed return to full athletic function in all cases at long‐term follow up (median 5 years; range 1.25‐9 years). Conclusion Tenoscopic decompression was an effective treatment for DFTS synoviocoeles, which, along with treatment of concurrent intrathecal injury, carried an excellent prognosis and avoided the need for resection via an extrasynovial approach.