This study was conducted to determine the relationship between selfefficacy and cooperation in the basketball team of SMAN 1 Sooko Mojokerto. The subjects used in this study were 16 members of the men's basketball team of SMAN 1 SOOKO aged 16-18 years. The research instrument used was the New General Self-Efficacy Scale (NGSE) to measure self-efficacy and the 5-item scale developed by Sharma ( 2012) to measure the level of teamwork in basketball. The data analysis technique in this study used the Pearson Product Moment Correlation statistical technique. The results of the study found the Pearson Correlation of the two variables (r = 0.961). This means that the two variables have a positive correlation direction.