Background: Working effectively in teams is an important 21st century skill as well as a fundamental component of the ABET professional competencies. However, successful teamwork is challenging, and empirical studies with adolescents concerning how the collaboration quality of team members is related to team performance are limited. Purpose/Hypothesis: This study investigated the relationship between team collaboration quality and team performance in a robotics competition using multiple measures of team performance, including both objective task performance and expert judge evaluations, on a diverse set of supporting performance dimensions. Design/Method: Data included Table Score, Robot Design, Research Project, Core Values, and Collaboration Quality scores for 366 youths on 61 K-8 robotics teams that participated in a FIRST LEGO League Championship. Regression and mediation analyses were conducted to explore the relation between effective team collaboration and team performance. Furthermore, analysis of variance was conducted to explore the relationship between Collaboration Quality and team experience. Results: Collaboration Quality was a good predictor of robotics team performance across all measures (with R[superscript 2] = 0.50 and p < 0.001). Mediation analysis revealed that the Robot Design acted as a full mediator for the predictive effect of Collaboration Quality on the Table Score. In addition, the cumulative amount of team experience was significantly related to Collaboration Quality. Conclusions: Overall, this study using collaboration performance assessments and actual competition data with a large number of teams confirms the importance of high-quality teamwork in producing superior products with students engaged in authentic engineering tasks.