OBJECTIVES: Excess chin and neck fat adversely affects facial appearance, producing measureable negative impacts on psychological health and psychosocial function. The Patient-Reported Submental Fat Impact Scale (PR-SMFIS) is a patient-reported outcome (PRO) measure developed and validated to assess submental fat (SMF)-associated psychological impact and its improvement associated with the reduction of SMF with deoxycholic acid (DCA) injection (ATX-101) as an injectable treatment for SMF. METHODS: Scale development and validation followed global regulatory guidelines and industry best practices. A conceptual model and draft response items were developed based on literature review, key opinion leader interviews, and patient concept elicitation interviews. The resulting 6-item scale assesses negative psychological impact of SMF on emotional perceptions (happiness, self-consciousness, bothersomeness, and embarrassment) and visual perceptions (looking older and overweight). Items are rated on an 11-point scale (0 = no impact, 10 = extreme negative impact); the total scale score is the average response. Six clinical trials of ATX-101 for SMF treatment provide assessments of reliability, construct validity, sensitivity to change, and score interpretation. PR-SMFIS validity was assessed using two generic measures of psychological impact, the Derriford Appearance Scale-24 (DAS-24) and Body Image Quality of Life Inventory (BIQLI). RESULTS: The PR-SMFIS demonstrated high test-retest reliability (Intra-class correlation = 0.75), internal consistency (Cronbach’s alpha › 0.92), external validity against the DAS-24 (r = 0.57) and BIQLI (r = -0.3), and patient SMF ratings (r = 0.49 to 0.75). SMF treatment produced large effect sizes (Cohen ES = -2) consistent with effect sizes for clinician and patient ratings, and objective measures of SMF reduction. CONCLUSIONS: These results confirm that PR-SMFIS is a content-valid PRO instrument with robust reliability and validity for SMF psychological impact assessment.