This study, published in Psychology of Well-Being, investigated whether an individual-level well-being assessment and scoring method (IWBS) could be adapted from the population-based Gallup-Healthways Well-Being Index to assess individual well-being across multiple domains (physical health, emotional health, healthy behaviors, work environment, basic access and overall life-evaluation). A total of 4,136 participants from 39 states were recruited through the internet for a clinical trial. Exploratory analyses were conducted on half the sample (n = 2036) using principal component analyses (PCA) with varimax rotation and confirmatory factor analysis was conducted on the second half of the sample (n = 2100) using structural equation modeling to validate the measurement model found by the PCA. The IWBS met each of the criteria that were established for measurement development. Findings indicated that there was initial support for using the IWBS to assess well-being at the individual level.