Purpose: To investigate risk factors for recurrent or new tumor in patients with conjunctival melanoma. Methods: Retrospective review of patients with conjunctival melanoma managed on the Ocular Oncology Service, Wills Eye Hospital from 1974 to 2019. Results: There were 540 patients with mean follow-up of 57.6 months, of whom 176 (33%) had recurrent or new tumor formation. Risk factors for recurrent or new tumor on univariate analysis included presentation at older age (OR: 1.02 [1.01–1.03] per 1-year increase in age, p = 0.002), history of prior conjunctival surgery (OR: 1.62 [1.05–2.49], p = 0.03), worse visual acuity at presentation (OR: 1.76 [1.04–2.98] per 1 log-unit increase, p = 0.04), more advanced AJCC clinical T-subcategory (OR: 1.08 [1.02–1.14] per 1 subcategory increase, p = 0.01), tumor primary location in tarsal conjunctiva (OR: 1.80 [1.09–2.98], p = 0.02), and secondary tumor involvement of the fornix (OR: 1.68 [1.06–2.65], p = 0.03), and eyelid (OR: 1.92 [1.07–3.43], p = 0.03). Risk factors on multivariate analysis using all demographics, clinical features, and tumor location included presentation at older age (OR: 1.02 [1.00–1.03], p = 0.01), history of prior conjunctival surgery (OR: 1.84 [1.16–2.94], p = 0.01), and more advanced AJCC clinical T-subcategory (OR: 1.07 [1.01–1.13] per one subcategory increase, p = 0.03). Conclusion: On multivariate analysis, the strongest predictors of recurrent or new tumor formation following treatment of conjunctival melanoma included older age, history of prior conjunctival surgery, and advanced AJCC T-subcategory. These results suggest that earlier detection and the first surgery in conjunctival melanoma management are critical for prevention of recurrent or new tumor, and we recommend prompt referral to an experienced surgeon.