BACKGROUND: Older adults treated with anticoagulants for atrial fibrillation (AF) or venous thromboembolism (VTE) face heightened bleeding risk, which can affect physical, emotional and social wellbeing and function. Existing instruments assess treatment satisfaction or generic quality of life but do not capture the specific impact of bleeding in this population. The goal of this study was to psychometrically validate HELIX (HEmorrhage Life Impact indeX), a novel patient-reported outcome (PRO) measure of bleeding-related quality of life in older adults on anticoagulation. METHODS: We enrolled adults aged ≥65 years with AF or VTE on oral anticoagulants. Psychometric testing of the previously derived, 19-item HELIX PRO included exploratory factor analysis, internal consistency (Cronbach's α), floor and ceiling effects, construct validity (correlations with PROMIS short forms), test-retest reliability (intraclass correlation coefficients), and responsiveness. RESULTS: Ninety-five participants (mean age 75, 45% women, 87% White; 66% AF, 33% VTE) participated. Factor analysis identified two subscales: bleeding symptoms (6 items) and quality of life (13 items). Internal consistency was high overall (α = 0.91), excellent for quality of life (α = 0.95), and acceptable for bleeding symptoms (α = 0.61). HELIX scores showed no floor or ceiling effects and demonstrated expected convergent and divergent validity with PROMIS measures. Test-retest reliability was good-to-excellent for most items. Responsiveness analysis suggested HELIX was more sensitive to within-person change than PROMIS. CONCLUSION: HELIX demonstrated strong initial psychometric performance as a bleeding-related quality of life instrument for older adults taking anticoagulants. It complements existing measures and warrants further validation in larger and more diverse populations to evaluate clinical utility and prognostic value.