PurposeTo analyze the clinical characteristics and long-term follow-up of patients with advanced ocular surface squamous cell carcinoma (OSSC) involving periocular tissues and/or orbit. Primary outcomes were overall survival (OS), disease-free survival (DFS), and overall recurrence rate (RR). Secondary outcomes were a correlation between primary outcomes and tumor location, American Joint Committee on Cancer Classification (AJCC) staging system, histological results, surgical margins, and type of treatment. Study design: a retrospective case series.MethodsThe medical records of patients affected by OSSC involving periocular tissues and/or orbit referring, from 01/2011 to 01/2020, to our tertiary referral center were reviewed.ResultsThirty-six eyes of 36 patients were included. The mean age was 68.2 years; 18 (50%) patients were males. The mean follow-up was 40 months. The RR was 64%. The OS at 12, 24, 36, and 60 months was respectively 97.1%, 92.7%, 92.7%, and 92.7%. The DFS at 12, 24, 36, and 60 months was respectively 62.9%, 50.8%, 41.6%, and 29.7%. Multicentric disease (p = 0.0039), inferior tarsus localization (p = 0.0428), histological diagnosis of high-risk SSCs (p = 0.0264), positive surgical margins (p = 0.0434), and excisional biopsy (EB) alone (p = 0.0005) were associated with an increased risk of recurrence. A shorter OS was observed in patients who underwent EB alone (p = 0.0049).ConclusionOSCC involving periocular tissues and/or orbit is an aggressive disease with a high recurrence rate. Multicentric disease, positive surgical margins, inferior tarsus localization, and surgery without adjuvant therapies are strong predictors of recurrence and are the main factors affecting prognosis.