Background: To compare 10-year treatment outcomes of radical prostatectomy (RP) vs external beam radiation therapy (EBRT) vs brachytherapy (BT) for patients with intermediate risk prostate cancer (IRPC). Methods: A retrospective analysis using propensity score matching was performed on 1,503 IRPC patients who underwent treatment from 2004 to 2007. 819 underwent RP, 574 underwent EBRT to a median dose of 75.3 Gray, and 110 underwent BT using iodine-125. Biochemical failure was defined by the American Urological Association (AUA) definition of prostate specific antigen (PSA) failure for RP patients, and the American Society of Therapeutic Radiology and Oncology (ASTRO) - Phoenix definition for the EBRT and BT patients. Results: Median follow up was 10.0 years for RP, 9.6 for EBRT, and 9.8 for BT (range 1.0-13.4 years). With RP 76.3% had Gleason score 7 vs 72.8% for EBRT vs 57.3% for BT, p = 0.0001. Median initial PSA was 7.4 for RP, 9.4 for EBRT, and 8.3 for BT, p < 0.0001. Neoadjuvant androgen deprivation therapy was given in 58.9% of EBRT patients vs 12.7% of BT vs 0.6% for RP, p < 0.0001. Only 14% of BT received supplemental external radiation. The 10-year freedom from biochemical failure (FFBF) was 82.0% for BT vs 58.0% for RP vs 58.8% for EBRT, p < 0.0001. Subset analysis of unfavorable IRPC patients showed a 10 year FFBF of 81.6% for BT vs 55.8% for RP vs 51.0% for EBRT, p < 0.0001. The 10-year freedom from salvage therapy was 89.5% for BT vs 64.0% for RP vs 73.4% for EBRT, p < 0.0001. There were no significant differences in distant metastases-free survival, prostate cancer-specific survival, or overall survival after adjusting for age. Multivariable analysis between pairwise groups with BT balanced by stabilized inverse probability of treatment weights showed that BT remained an independent predictor for improved FFBF, p = 0.049 for BT vs EBRT, and p < 0.0001 for BT vs RP. Conclusions: Brachytherapy using iodine-125 is a reasonable treatment option for IRPC patients. Although BT showed improved FFBF after propensity score matching, this did not impact overall survival.