OBJECTIVE: The aim of the present study was to psychometrically test and validate the Well-being Coaching Inventory (WCI), a proposed measure of interconnected, whole-person well-being in the context of health and wellness coaching (HWC). METHODS: Initially 49 items, the WCI was conceived with 4 dimensions: Mind, Body, Work, and Life. The inventory was evaluated in 3 sequential studies to test: (a) face validity, (b) convergent validity, and (c) predictive validity. Expert judgment, correlational analyses, and factor analyses were techniques applied to collected WCI data. RESULTS: After statistical evaluation (n = 261) of fit to each dimension, the WCI was shortened to 20 items that demonstrated convergent validity. Further use of confirmatory factor analyses and exploratory structural equation model in a large sample study (n = 531) provided additional support for the inventory's convergent validity. Through correlation analyses to theoretically related concepts predictive validity was established. CONCLUSIONS: The WCI is a valid, applicable, and reliable scale for use in HWC research and practice. It is an instrument that will aid HWC practitioners and researchers as a central outcome measure for their practice.