Parents play a central role in children’s ongoing participation and enjoyment of sport. Despite compelling evidence that parental behaviour can undermine the quality of children’s experiences in sport, little research has examined whether strategies to support parents to engage in positive sports parenting behaviour are effective. In this paper, we report two studies that had the overall aim of developing, implementing and evaluating a program designed to promote positive parental involvement and improve spectator behaviour in junior rugby league in Australia. Study 1 involved the development of a prototype version of the program, named Play Well Triple P, which was qualitatively evaluated through interviews with 19 parents about their satisfaction with the program. In Study 2, we used feedback from Study 1 to refine the program and develop a pilot version, which was then evaluated in a quasi-experimental feasibility study with 101 parents (mean age = 38.42 years; 72% mothers) of junior rugby league players. The pilot version involved one interactive online module and text messages to reinforce content and prompt strategy implementation across the season. Participation in Play Well Triple P was associated with increased positive sports parenting behaviour and reduced controlling and intrusive sports parenting behaviour, with a trend towards reducing over-reactive parenting practices at home. These findings are discussed in relation to the feasibility of implementing a brief and engaging sports parenting intervention in the context of a broader integrated system designed to facilitate ongoing participation of children in sport.