Background: Caring for loved ones with cancer can be burdensome and emotionally demanding; screening for caregiver depression and anxiety can mitigate the risks of under-identifying and undertreating these conditions. CancerSupportSource®-Caregiver (CSS-CG) is a 33-item multidimensional distress screening and referral program with items related to depression (feeling sad or depressed; feeling lonely or isolated) and anxiety (feeling nervous or afraid; worry about the future and what lies ahead). We evaluated the psychometric performance of CSS-CG depression (CSS-D2) and anxiety (CSS-A2) risk screening subscales among community-based family and informal caregivers. Methods: 328 cancer caregivers enrolled in Cancer Support Community’s Cancer Experience Registry and rated CSS-CG items (0=Not at all; 4=Very seriously), PROMIS-29 v2.0 Depression & Anxiety Short Forms 4a (PROMIS-D; PROMIS-A), and PHQ-2 Depression & GAD-2 Anxiety. We calculated Pearson correlations; area under the curve (AUC) with PROMIS-D T-score ≥60 and PHQ-2 ≥3 to flag depression risk, and PROMIS-A T≥62 and GAD-2 ≥3 for anxiety risk; and calculated sensitivity/specificity and positive/negative predictive values (PPV/NPV) with cut-scores of ≥3 for each CSS-CG risk scale. Results: 55% of caregivers were identified as at risk for clinically significant depression, 68% for anxiety. Regarding comorbid risk: 50% both, 4% depression only, 18% anxiety only. CSS-D2 was correlated with PROMIS-D (r=.76; p<.001), AUC=.879, sensitivity=.95/specificity=.67, NPV=.96/PPV=.60; and also with PHQ-2 (r=.61; p<.001), AUC=.868, sensitivity=.93/specificity=.63, NPV=.95/PPV=.54. CSS-A2 was correlated with PROMIS-A (r=.79; p<.001), AUC=.879, sensitivity=.95/specificity=.54, NPV=.93/PPV=.63; and also with GAD-2 (r=.62; p<.001), AUC=.867, sensitivity=.98/specificity=.51, NPV=.97/PPV=.43. Conclusions: CSS-CG depression and anxiety risk subscales demonstrated good concurrent validity and sensitivity among cancer caregivers, with lower specificity. Embedding clinical risk screening within the broader CSS-CG screening and referral program provides flexibility in assessing unmet caregiver needs and clinical distress while minimizing burden. In implementation of CSS, follow-up procedures should be well-defined for individuals who screen positive. Future work will evaluate psychometric support for a shortened CSS-CG tool and should examine CSS-CG risk scales against structured diagnostic interviews.