While regular exercise is associated with a number of physical and mental health benefits, basing one’s self-esteem largely on exercise is likely associated with negative outcomes. In the present studies, the authors developed a novel measure of this construct, something they term “exercise overvaluation.” In Study 1, 820 participants completed an online survey measuring self-esteem, exercise attitudes and behaviors, and eating disorder symptoms. Exploratory and confirmatory factor analysis were employed to develop the 14-item Exercise Overvaluation Scale. The results provided evidence of discriminant and convergent validity and internal consistency reliability of scale scores. In Study 2, the Exercise Overvaluation Scale was administered to 134 university athletes, including those who participated in intramural sports, club sports, and collegiate athletics. The results from Study 2 supported the criterion validity and test–retest reliability of scale scores. This scale offers researchers a new tool to help understand the relationships among exercise, self-esteem, and physical and mental health outcomes.