ABSTRACT Flourishing has been a focus of positive psychology, with increased attention to its translation into psychotherapy practice. Flourishing is an emergent process manifested in momentary experiential states characterized by positive emotions. A conceptualization of flourishing as an innate potential that psychotherapeutic interventions can help cultivate informs the development of this scale. The current study details the development of the Moments of Flourishing Experience Scale (MFES), a 23-item scale. The data were obtained from four different studies involving a total of 1472 adults (normative sample n = 1312; clinical sample n = 160). A bifactor model with four distinct positive affective experience subscales, yielded by factor analysis and then supported by a confirmatory factor analysis, was as follows: Calm & Self-Acceptance; Vitality; Generosity of Spirit & Gratitude; and Connection & Purpose. Across studies, the MFES showed discriminant validity from psychopathology measures and convergent validity with positive psychological functioning measures. The overall scale, as well as each of four subscales, also demonstrated strong reliability in both general and clinical populations. The MFES has initial psychometric support for the study of flourishing and shows promise as a tool to study flourishing as both outcome and process in psychotherapy.