Background: CancerSupportSource (CSS) is a 25-item distress screening tool implemented at community-based cancer support organizations and hospitals nationwide. CSS assesses distress over 5 domains: (1) emotional concerns (including depression and anxiety risk screening subscales), (2) symptom burden, (3) body and healthy lifestyle, (4) healthcare team communication, and (5) relationships. This study developed a short form of CSS and examined its psychometric properties. Methods: 2,379 cancer survivors enrolled in the Cancer Support Community’s Cancer Experience Registry. Participants provided demographic and clinical background and completed CSS-25 and PROMIS-29, a measure of health-related quality of life. Item reduction was conducted with a subsample of 1,435 survivors and included external item quality (correlations between items and PROMIS-29 scales), internal item quality (inter-item and inter-factor correlations, factor loadings and structure, and item communalities from an exploratory factor analysis of CSS-25), and professional judgement (ranking/prioritization of items by CSS-25 developers, accounting for theoretical and practical implications). Pearson correlations and confirmatory factor analysis were conducted on a separate subsample of 944 survivors to corroborate psychometric properties and dimensionality of the shortened scale. Results: Scale refinement resulted in a 15-item short form of CSS (CSS-15). At least 1 item from each of the 5 CSS-25 domains was retained to preserve multidimensionality, including anxiety and depression risk screening subscale items. Additionally, 1 item about tobacco/substance use was kept due to clinical significance for risk assessment. In confirmatory factor analysis, the model explained 59% of the variance and demonstrated good fit (RMSEA=0.068, 90% CI=0.061–0.075; SRMR=0.033; CFI=0.959; χ2(68)=334.75, P<.001). Correlation between CSS-15 and CSS-25 was 0.986, P<.001. Total distress was associated with PROMIS subscales (rs=−.65–.75, ps<.001); internal consistency reliability was excellent (α=.92). Conclusions: CSS-15 is a brief, reliable, and valid multidimensional measure of distress. The reduced measure retained excellent internal consistency and a stable factor structure, while correlating well with CSS-25 and PROMIS-29. CSS-15 can serve as a practical tool to efficiently screen for distress among cancer patients and survivors.