Background: Internal health locus of control has been associated with positive health outcomes and behaviors. Understanding the mechanisms of this relationship are key to designing and implementing effective health behavior intervention programs. Purpose: The purpose was to examine whether self-efficacy and social support mediate the relationship between college students' health locus of control and the health behaviors of physical activity, fruit and vegetable intake, and dietary fat intake. Methods: Eight hundred thirty-eight college students at 2 public universities in the southeastern United States completed online surveys of health locus of control, physical activity, fruit and vegetable intake, and dietary fat and self-efficacy and social support of those behaviors from July to September 2013. Mediation was tested with product of coefficients approach. Results: Self-efficacy and social support mediated the relationship between health locus of control and physical activity behaviors and fruit and vegetable intake. Only self-efficacy was a mediator for dietary fat intake. Discussion: Internal health locus of control appears to exert its influence on health behaviors, at least partially, through self-efficacy and social support. Translation to Health Education Practice: By understanding the role of self-efficacy and social support, practitioners can develop and implement interventions that target improving locus of control for health behaviors.