Prostate cancer is a heterogeneous disease whose therapies frequently have adverse effects. Informed patient counseling regarding likely clinical outcomes is therefore important. In this systematic review we aimed to identify all external validations of tools that are used to predict clinical outcomes in patients undergoing radical prostatectomy and evaluate which are optimum for clinical implementation. PubMed and EMBASE were searched from 2007 to 2016. Search terms related to the inclusion criteria were: prostate cancer, clinical outcomes, radical prostatectomy, and prognosis. Titles and abstracts were screened and relevant studies were advanced to full-text review. Reference lists were reviewed for further studies. The Centre for Evidence Based Medicine prognostic tool was used for critical appraisal. Seventy-three studies externally validated 13 pre- and 41 postoperative tools for the prediction of biochemical recurrence (BCR), aggressive BCR, metastasis, and prostate cancer-specific mortality (PCSM). Recommendations for clinical implementation were made on the basis of accuracy, cohort sizes, and consistency. The accuracy of recommended tools ranged from 68% to 79% and 72% to 92% among the largest validation cohorts for pre- and postoperative tools. For preoperative prognosis we recommended the Cancer of the Prostate Risk Assessment (CAPRA) and Stephenson nomograms for BCR, the CAPRA nomogram for aggressive BCR as well as metastasis, and the D'Amico criteria for PCSM. For postoperative prognosis we recommended the CAPRA-Surgery (CAPRA-S), Stephenson, Kattan, Duke prostate cancer (DPC), and the Suardi nomograms for the prediction of BCR, the DPC nomogram for aggressive BCR, the CAPRA-S and Eggener nomograms for metastasis, and the Eggener nomogram for PCSM. Use of these tools should help clinicians deliver accurate, evidence-based counseling to patients undergoing prostatectomy.