ABSTRACT Relationships between conscientiousness-related traits and transtheoretical model (TTM) of change constructs, exercise self-efficacy, and exercise behavior were examined in college and community samples (N=566). Measures of the conscientiousness-related traits of conventionality and industriousness were expected to show positive relations with measures of exercise behavior stage location, processes of exercise behavior change, endorsing the benefits of exercise behavior (i.e., decisional balance), exercise self-efficacy, and self-reported exercise behavior. In addition, based on Neo-Socioanalytic Theory (Roberts & Wood, 2006) an intervening role was predicted for TTM constructs and exercise self-efficacy in the relationship between conscientiousness-related traits and exercise behavior stage location. The results showed industriousness (being hardworking) to be the most robust conscientiousness-related predictor of stage location, processes of change, endorsing the benefits of exercise behavior, and exercise self-efficacy. Mediation analyses showed the relationship between industriousness and exercise behavior stage location to be fully accounted for by select processes of change and exercise self-efficacy scales. The results are discussed in terms of a useful integration of trait and social-cognitive approaches to exercise behavior, with an emphasis on the role of industriousness as an important individual difference factor therein.