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PURPOSE This study aims to quantify the risks of cataract surgery in patients who have previously undergone external beam radiotherapy (EBRT). Cataract is a side effect of this treatment, and the risk of complications following cataract surgery in this cohort is poorly understood. SETTING Tertiary ophthalmology and oncology hospital. DESIGN Retrospective case series. METHODS Patients treated with orbital EBRT at the Beatson West of Scotland Cancer Centre between 2001 and 2019 were identified, and clinical records were reviewed to identify those who had subsequently undergone cataract surgery. Pre- and post-operative case records, and operation records, were reviewed to identify demographic data, and data regarding complications and surgical outcomes. RESULTS Forty-six eyes (of 33 patients) were included in this study. The indications for EBRT included thyroid eye disease, lymphoma, choroidal metastases and other orbital malignancies. Mean corrected pre-operative Snellen visual acuity (VA) was 20/100 (range 20/30-20/2000) improving to 20/25 (20/12 to 20/160, one-way ANOVA p<0.01). Mean visual gain was 0.5 LogMAR (-0.9 to 1.9). There was one case of posterior capsule (PC) rupture with vitreous loss (2%). Dense PC plaque was noted intra-operatively in 19.5% (n=9). 13% (n=6) required Nd:YAG laser posterior capsulotomy. There were six cases (13%) of cystoid macular oedema (CMO). CONCLUSION Visual outcomes following cataract surgery are similar in this cohort of patients to those obtained in a nationwide cohort. EBRT seems to be associated with an increased incidence of intra-operative PC plaque, post-operative CMO (which in most cases settled with treatment), and need for posterior capsulotomy.