The Systemic Clinical Outcome and Routine Evaluation version 15 (SCORE-15) is an assessment used to assess for clinical change in family functioning. The SCORE-15 has been demonstrated in the past to be a reliable and valid measure for assessing for clinical change and is largely used throughout the UK. However, the SCORE-15 lacks the ability to determine whether an individual's change in family functioning is clinically significant. This study aims to establish a reliable change index and clinical cutoff score based on a US sample so that researchers and clinicians can determine clinically significant change. A sample of 63 clinical participants and 244 community participants completed the SCORE-15, including 165 community participants who completed the SCORE-15 a second time. Results established a cutoff of 51.92 and a reliable change index of 17.51 for the SCORE-15. This indicates that therapy clients who improve their SCORE-15 score by at least 17.5 points and who cross the threshold of 52 during the course of therapy are considered to have experienced clinical significant improvement.