Millions of children and adolescents attend summer camp every year. Previous research has shown attending camp results in positive youth development outcomes, but there is currently little known about camp and camper-related factors that may moderate these outcomes. The current study investigated how campers' sense of belonging with camp and their perceived relationships with camp counselors affected positive youth development outcomes. More specifically, the hypotheses of the current study investigated the roles of sense of belonging and relationship (with camp counselor), and the interaction between these two constructs, on positive youth development outcomes. Furthermore, hypotheses in the current study investigated the moderating effects of age, gender, and camp type on the associations between sense of belonging and relationships on positive youth development outcomes. Data were gathered from 112 campers before and after attending one of two summer sessions of YMCA of San Diego's Camp Surf. Results showed statistically significant positive pre-post changes in identity, independence, making friends, insecurity, peer relationships, leadership, positive values and decision making, adventure and exploration. Sense of belonging at camp was significantly associated with pre-post differences for positive identity (p = 0.001), peer relationships (p = 0.001), and adventure and exploration participation (p = 0.029). Relationship with camp counselors was significantly associated with pre-post differences for positive values and decision-making (p < 0.001) and environment (p = 0.006). Furthermore, the interaction between sense of belonging and relationship with camp counselors was significant for independence (p < 0.001) and insecurity (p < 0.001). There was a moderating effect of camp type on the relationship between sense of belonging and making friends (p = 0.038), and sense of belonging and adventure and exploration enjoyment (p = 0.016), but there were no moderating effects of age or gender. Based on these findings, YMCA Camp Surf resulted in positive youth development outcomes in campers. For some aspects of positive youth development, campers experienced differential outcomes based on their sense of belonging with camp, relationship with camp counselors, and camp type. These results contribute to the positive youth development literature by providing preliminary evidence on how psychological constructs apply to the camp setting. In addition, camp staff and administrators can use these results to help provide campers with an optimal camp experience by focusing resources towards emphasizing campers' sense of belonging with camp and relationships with camp counselors. Future studies can use better measurement tools and comparison groups to provide further evidence on the roles of sense of belonging and relationship with camp counselors, as well as other psychological constructs, on camp outcomes.