--- - |2+ Abstract Objective Fear of cancer recurrence (FCR) is one of the major existential unmet needs of cancer survivors. Due to growing availability of evidenced‐based interventions for high FCR, valid and reliable brief measures of FCR are needed. This study aimed to validate the 6‐item Cancer Worry Scale (CWS) and to establish a cut‐off score for high FCR. Methods Participants in this study were 1033 cancer survivors and patients recruited as part of 5 existing studies on FCR involving patients and survivors with gastro‐intestinal stromal tumors, colorectal, breast, and prostate cancer. De‐identified data of the CWS, Fear of Cancer Recurrence Inventory (FCRI), Impact of Event Scale, Hospital Anxiety and Depression Scale, and EORTC‐QLQ‐C30 were amalgamated for the analyses. Confirmatory factor analysis of the CWS was performed. Sensitivity and specificity were tested with the FCRI as gold standard. Results Results confirmed that the 6‐item version of the CWS maintained good construct validity, convergent and divergent validity, and high internal consistency (α 0.90). The optimal cut‐off for the 6‐item CWS was 9 versus 10 using the 12 vs 13 FCRI‐SF score (sensitivity 82%, specificity 83%) and the 15 vs 16 FCRI‐SF score (sensitivity 88%, specificity 73%). Using the highest FCRI‐SF cut‐off (21 vs 22), the optimal CWS cut‐off was 11 vs 12 (sensitivity 88%, specificity 81%). Conclusions The present results provide researchers and clinicians with a brief valid and reliable measure of FCR which is suitable for measuring FCR in cancer patients and survivors. - Psycho-Oncology, EarlyView.