Competing demands in coaching duties hinder coaches from effecting Positive Youth Development (PYD) among athletes. While research has documented how supporting staff in youth sport teams can help coaches facilitate PYD, such studies have been scarce and brief in discussing how they impact PYD among high school athletes. The present study examined the roles supporting staff can play and their contributions to PYD in high school sports. Eight high school sport teams (48 athletes, 8 coaches, 8 teachers) were recruited through purposive sampling. Coaches, athletes and supporting staff from each team were interviewed for a comprehensive account of the research interest. Thematic analysis of the interview transcripts yielded the main themes of: 1) roles played by supporting staff in youth sport teams, 2) their contributions to PYD, and 3) advantages over sport coaches in promoting PYD. Results suggest that supporting staff complement coaches in promoting PYD and may be in more advantageous positions to impact some areas of PYD in high school sports. We additionally highlighted important benefits of having school educators support youth sport teams. Considering the study’s limitations, this paper discussed implications of the findings and provided recommendations for coach education and practice in high school sports.