When an individual enters the Criminal Justice System there is a belief and expectation that they will change from the individual who perpetrated the crime(s) to a law-abiding citizen. However, there are currently few measures of Justice-Involved Person (JIP) change that have established validity predicting post-program or post-release outcomes. The purpose of this research was to validate a new measure of JIP change, the Client Change Scale (CCS), with a sample of 390 JIPs on community supervision by the Correctional Service of Canada (CSC). The mixed method, retrospective file reviews suggests that the CCS reflects acceptable psychometric properties, predicts, and in some cases incrementally predicts, post-release outcomes. It also has utility predicting supervision type and differentiating based on program completion. The qualitative findings suggests that the information available at CSC is sufficient for scoring the CCS. The results are promising and support prospective studies using the CCS.