The main aim of the present study was to examine the mediation effect of sport self-efficacy on the relationship between dimensions of perfectionism and competitive anxiety in a sample of Iranian athletes. 233 volunteer athletes (145 boys, 88 girls) from different sport fields participated in this study. All participants were required to complete the Competitive Perfectionism Scale (CPS), the Multidimensional Competitive Anxiety Questionnaire (MCAQ) and the Sport Self – Efficacy Scale (SSES). The results revealed that striving for perfection (positive perfectionism) was negatively associated with cognitive and somatic anxiety, and positively associated with self – confidence. The results also revealed that negative reaction to imperfection (negative perfectionism) was positively associated with cognitive and somatic anxiety, and negatively associated with self – confidence. Analysis of the data revealed that sport self – efficacy mediated the relationship between positive and negative dimensions of perfectionism and competitive anxiety.