Most men diagnosed with very-low and low-risk prostate cancer are candidates for active surveillance; however, there is still a misclassification risk. We examined whether PI-RADS category 4 or 5 combined with ISUP 1 on prostate biopsy predicts upgrading and/or adverse pathology at radical prostatectomy.A total of 127 patients had ISUP 1 cancer on biopsy after multiparametric MRI (mpMRI) and then underwent radical prostatectomy. We then evaluated them for ISUP upgrading and/or adverse pathology on radical prostatectomy.Eight-nine patients (70%) were diagnosed with PI-RADS 4 or 5 lesions. ISUP upgrading was significantly higher among patients with PI-RADS 4-5 lesions (84%) compared to patients with equivocal or non-suspicious mpMRI findings (26%, p < 0.001). Both PI-RADS 4-5 lesions (OR 24.3, 95% CI 7.3, 80.5, p < 0.001) and stage T2 on DRE (OR 5.9, 95% CI 1.2, 29.4, p = 0.03) were independent predictors of upgrading on multivariate logistic regression analysis. Men with PI-RADS 4-5 lesions also had significantly more extra-prostatic extension (51% vs. 3%, p < 0.001) and positive surgical margins (16% vs. 3%. p = 0.03). The only independent predictor of adverse pathology was PI-RADS 4-5 (OR 21.7, 95% CI 4.8, 99, p < 0.001).PI-RADS 4 or 5 lesions on mpMRI were strong independent predictors of upgrading and adverse pathology. Incorporating mpMRI findings when selecting patients for active surveillance must be further evaluated in future studies.