Objective: This research aims to examine team cohesion beliefs of youth athletes based on gender and team tenure, and team cohesion-collective efficacy relationship in youth sport. Material and Methods: The participants were 180 males (age: 15.41±1.15 year) and 70 females (age: 14.70±1.09 year), 250 athletes in total (age: 15.10±1.16 year), involved youth academies for team sports (football, basketball and volleyball). The Collective Efficacy Scale and Youth Sport Environment Questionnaire were used to assess the athletes’ collective efficacy beliefs and perceptions of team cohesion. Descriptive statistics, one-way MANOVA, one-way ANOVA, Pearson Moment correlations, multiple regression and bootstrapping procedures were used to analyze the research data. Results: Results showed significant differences on both the task and social dimensions of team cohesion based on the gender of participants (p< 0.05). Team cohesion beliefs did not differ based on team tenure (p> 0.05). Significant negative correlations were observed between task cohesion and collective efficacy (r=-0.312, p< 0.01) and between social cohesion and collective efficacy (r=-0.149, p< 0.05). An indirect effect of social cohesion on collective efficacy through task cohesion was observed (β=-0.05, BCa 95% CI=[-0.08 to-0.03]). Conclusion: The findings of this study suggest that high social cohesion may have adverse effects on collective efficacy in youth sport settings.