Self-efficacy and causal attributions were examined as mediators of perceived psychological momentum. Participants were randomly assigned to either a repeated success or a repeated failure group in which success or failure was manipulated by having participants compete against a highly skilled confederate. Each participant and confederate performed three sets of 10 basketball free throws. Free throw self-efficacy, perceived psychological momentum, and causal dimensions were assessed after each set. Results indicated that the success and failure manipulations were effective in that the responses changed differently over time for both groups. Experiencing competitive success increased perceptions of momentum; experiencing competitive failure decreased perceptions of momentum. In contrast, self-efficacy only changed in response to competitive success as the participants became more confident. Both groups attributed the competitive outcome to internal, personally controllable, and unstable causes.