Purpose: To investigate the quality of life (QoL) after different treatment modalities for low-risk prostate cancer, including brachytherapy, robot-assisted laparoscopic prostatectomy (RALP), and active surveillance (AS) with validated questionnaires. Materials and Methods: From a prospective database, we selected a total of 144 men with low-grade localized prostate cancer including 65 (45.1%) patients with RALP, 29 (20.2%) with brachytherapy, and 50 (34.7%) whose cancer was managed with AS. QoL was routinely evaluated with validated questionnaires: The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC-QLQ-C30), EORTC-QLQ-Prostate Module (PR)25, International Index of Erectile Function (IIEF)-15, International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) with a minimum follow-up of 1 year. Results: In comparison with baseline scores, the brachytherapy group showed a significant decrease of QoL domain scores of voiding complaints (P=0.010), use of incontinence aids (P=0.011), sexual functioning domain (P=0.011), and erectile function (P0.001). In the RALP group, sexual function (P0.001), incontinence (P0.001), and erectile function were significantly affected. A decrease in sexual function was observed in 71% of men after RALP and 59% after brachytherapy. In 30% of men under AS, a decrease of erectile function score during follow-up was reported. Overall, no significant decrease in general QoL was observed neither for men under AS nor for men treated by brachytherapy or RALP. Clinical factors such as age, prostate size, prostate-specific antigen level, and nerve preservation during RALP were nonpredictive of overall QoL after treatment for the individual patient (P=0.676). Conclusion: Patients with low-risk prostate cancer who are treated with brachytherapy or RALP report deterioration of QoL of specific domains such as voiding, continence, and sexual functioning in comparison with AS patients. A decrease of erectile function was also observed during AS. Overall QoL was similar for all three treatments options.