Background/Aims. To report the safety and efficacy of strontium (Sr90) beta radiotherapy as adjuvant treatment for conjunctival melanoma. Methods. A retrospective cohort study was undertaken from 1999 to 2007 of all patients who underwent Sr90 beta radiotherapy for incompletely excised conjunctival melanoma. Failure of treatment was defined as recurrence of a conjunctival melanoma at the same location following beta radiotherapy. Results. Twenty patients underwent Sr90 beta radiotherapy for incompletely excised conjunctival melanoma. Median follow-up interval was 59 months (8–152). All patients had conjunctival melanoma involving the bulbar conjunctiva. Underlying diagnoses included PAM with atypia in 60% (12 of 20), PAM without atypia in 15% (3 of 20), and de novo conjunctival melanoma in 25% (5 of 20). Following Sr90 beta radiotherapy, in 90% (18 out of 20) local control was achieved and visual acuity was not affected in any patient. Three patients (15%) had dry eye symptoms, episcleritis, and descemetcoele, respectively. No cataract or secondary glaucoma was reported. Conclusions. Sr90 treatment is a very effective adjuvant treatment after excisional biopsy and cryotherapy for conjunctival melanoma with a local success rate of 90%. The treatment is not associated with significant side effects and visual acuity is not affected.