Although philosophers and theologians have emphasized the centrality of inner peace for the good life, this concept has not generally been included in research on human flourishing. The authors argue that inner peace contributes to a more complete form of flourishing for both religious and secular people. They then propose a new instrument, the Inner Peace Scale, to measure inner peace, and they provide an initial psychometric evaluation of the instrument based on five empirical studies. The authors distinguish their scale from related measures, such as contentment, serenity, or tranquility. Engagement with literature from the social sciences and the humanities, along with the authors’ research findings, suggest that inner peace is comprised of three dimensions: acceptance of loss, transcendence of hedonism and materialism, and inner balance and calmness. Greater attention to the dimension of transcending hedonism and materialism may prove especially helpful in advancing the field, particularly in consumeristic societies.