Purpose: To assess the effect of proton magnetic resonance spectroscopy imaging (MRSI) on the accuracy of multiparametric magnetic resonance imaging (mpMRI) at 3 T for prostate cancer detection. Materials and Methods: Thirty-four patients with prostate cancer were included in this retrospective study. All patients underwent preoperative mpMRI on a 3-T scanner before radical prostatectomy. Magnetic resonance imaging evaluation was based on the prostate imaging-reporting and data system classification system. The accuracy of mpMRI with and without MRSI was determined using receiver operating characteristic analysis, with histology as the reference standard. Results: Multiparametric MRI including MRSI had a sensitivity of 57.0% and a specificity of 89.2% for sextant-based cancer detection. Multiparametric MRI without MRSI had a sensitivity of 58.1% and a specificity of 87.4%. There was no significant difference regarding the accuracy of mpMRI with and without MRSI (P = 0.48). Conclusion: The addition of MRSI does not improve the accuracy of 3 T mpMRI for sextant localization of prostate cancer.