ABSTRACT: OBJECTIVE:Self-efficacy expectations are associated with improvements in problematic outcomes widely considered clinically significant (ie, emotional distress, fatigue, and pain), related to positive health behaviors, and as a type of personal agency, inherently valuable. Self-efficacy expectancies, estimates of confidence to execute behaviors, are important in that changes in self-efficacy expectations are positively related to future behaviors that promote health and well-being. The current meta-analysis investigated the impact of psychological interventions on self-efficacy expectations for a variety of health behaviors among cancer patients. METHODS:Ovid Medline, PsycINFO, CINAHL, EMBASE, Cochrane Library, and Web of Science were searched with specific search terms for identifying randomized controlled trials (RCTs) that focused on psychologically based interventions. Included studies had (a) an adult cancer sample, (b) a self-efficacy expectation measure of specific behaviors, and (c) an RCT design. Standard screening and reliability procedures were used for selecting and coding studies. Coding included theoretically informed moderator variables. RESULTS:Across 79 RCTs, 223 effect sizes, and 8678 participants, the weighted average effect of self-efficacy expectations was estimated as g = 0.274 (P < .001). Consistent with the self-efficacy theory, the average effect for in-person intervention delivery (g = 0.329) was significantly greater than for all other formats (g = 0.154, P = .023; eg, audiovisual, print, telephone, and Web/internet). CONCLUSIONS:The results establish the impact of psychological interventions on self-efficacy expectations as comparable in effect size with commonly reported outcomes (distress, fatigue, pain). Additionally, the result that in-person interventions achieved the largest effect is supported by the social learning theory and could inform research related to the development and evaluation of interventions.