Primary ocular adnexal extranodal marginal zone mucosa-associated lymphoid tissue lymphoma (OAML) is a rare subtype of non-Hodgkin's lymphoma, and no consensus has been defined concerning the optimal treatment strategies. This study aims to investigate the associations of disease characteristics and different treatments with long-term outcomes of patients with localized OAML.A large retrospective cohort study was conducted in a single-center of China, and 166 patients with newly diagnosed primary localized OAML were enrolled. Detailed data of disease characteristics at diagnosis and treatments were collected for all patients. We compared treatment response and progression-free survival (PFS) among patients with different characteristics and treatments.Of the 166 patients, 52 received complete resection of neoplasm, whereas 114 had residual lesion after surgery. Among the 114 patients, 61 underwent watchful waiting and 53 received further treatment including localized radiotherapy, chemotherapy, or combined radiotherapy and chemotherapy. Median follow-up was 49 months. A total of 31 patients had disease progression or relapse, including four patients with such event more than five years after initial treatment. The 5-year PFS was 73.9%, 70.6%, and 85.9%, whereas the 10-year PFS was 69.3%, 59.2%, and 79.3%, among patients with complete resection of neoplasm, patients in the watchful waiting group and patients with further treatment, respectively. Patients with further treatment had longer PFS, compared with patients in the watchful waiting group (p = 0.011). Bilateral involvement at diagnosis was associated with significantly inferior PFS (p = 0.029), whereas age, IPI score, or TNM staging were not associated with PFS. No serious adverse reaction was reported among patients with further treatment.Bilateral involvement was associated with poor prognosis. Among patients with residual lesions after surgery, further treatment was associated with improved survival. Patients with OAML might experience disease progression or relapse more than five years after initial treatment.© 2022 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.