Objective: To report the outcomes and late toxicities in younger patients with long-term follow-up treated with brachytherapy with or without external beam radiotherapy for prostate adenocarcinoma. Materials and Methods: Patients treated with brachytherapy with or without external beam radiotherapy who were aged ≤60 years at treatment with ≥10 years of follow-up were selected from our database. The outcomes were analyzed regarding biochemical failure, distant metastases, and cause of death. Genitourinary outcomes were assessed using the International Prostate Symptom Score, Radiation Therapy Oncology Group, and Common Terminology Criteria for Adverse Events criteria. Gastrointestinal toxicity was measured using Radiation Therapy Oncology Group scales. Erectile dysfunction was measured using Sexual Health Inventory for Men and the Mount Sinai Erectile Function score. Results: A total of 131 patients met the inclusion criteria, with a median age of 57 years at treatment and a median follow-up of 11.5 years. Of the patients in this cohort, 9.9% developed biochemical failure with 1 failure and 1 prostate cancer-related death after 10 years. The International Prostate Symptom Score were statistically unchanged after 10 years. Of 22 cases (17%) of grade 2 or greater genitourinary toxicities, only 6 (4.5%) continued after 10 years. Of 11 cases (8.3%) of grade 2 or greater gastrointestinal events, none persisted past 10 years. A significant decrease occurred in the mean Sexual Health Inventory for Men score from 19.5 to 15.3 (P =.008). Of the potent patients before treatment, 69% remained potent at last follow-up. A total of 4 second malignancies were detected, 2 of which were within the radiation field. Conclusion: Men <60 years old who underwent brachytherapy for prostate cancer can expect minimal late genitourinary and gastrointestinal toxicity after 10 years and excellent potency preservation.