Background: To report long-term outcomes of magnetic resonance image-guided partial prostate brachytherapy of the peripheral zone. Methods: We conducted an institutional-board approved retrospective review of all men who underwent 0.5 Tesla GE Signa SP MRI-guided partial prostate brachytherapy to the peripheral zone. We estimated actuarial rates of biochemical progression (nadir +2 definition), as well as cumulative incidences of biopsy proven local recurrence, distant metastasis, and prostate cancer specific mortality. Fine and Gray’s competing risk regression was utilized in order to evaluate clinical factors associated with times to metastasis and prostate cancer specific mortality. Results: Between 1997 and 2008, 354 men underwent MRI-guided partial prostate brachytherapy. The numbers of patients with low and intermediate risk disease were 295 (83%) and 59 (17%), respectively. Sixty-seven (19%) patients received supplemental external beam radiotherapy. The median follow-up was 8.6 years. For National Cancer Center Network (NCCN) low risk-disease, 8-year estimates of biochemical progression, local recurrence, metastasis, and prostate cancer specific mortality were 23.5% (17.4-29.1), 6.4% (3.6-10.2), 2.0% (0.6-4.8), and 0%. Corresponding estimates for intermediate risk disease were 51.2% (31.3-65.4), 21.2% (10.2-34.9), 6.6% (1.7-16.3), and 5.4% (0.9-16.2). Twenty of 45 biopsy proven local recurrences occurred outside of the implanted peripheral zone. Of the 22 patients who developed distant metastases, 14 events occurred more than 10 years from therapy. On multivariate analyses, biopsy proven local recurrence was the only factor to demonstrate a significant association with metastasis (hazard ratio 2.50; p = 0.05) and a trend with prostate cancer specific mortality (5.02; p = 0.09). Conclusions: MRI-guided partial prostate brachytherapy to the peripheral zone in men with favorable risk prostate cancer is suboptimal with respect to long term cancer control outcomes. Additional studies using contemporary MRI techniques including 3 Tesla based multi-parametric imaging and fusion biopsy may lead to improved outcomes.