By the age of 8 years, boys experience body dissatisfaction and use strategies to become thinner and more muscular. The factors contributing to these outcomes are not well understood. This study examines boys’ investment in masculine gender norms and how this relates to their body esteem and their use of body change strategies. Participants were 321 boys aged 7 to 11 years in Melbourne, Australia. The results indicated that boys are invested in masculine physical ideals of strength and athleticism. Investment in these masculine ideals predicted boys’ use of body change strategies. In addition, investment in masculine gender norms moderated the relationship between pressures from peers and boys’ use of body change strategies. The findings highlight the importance of gender norms in shaping boys’ body change strategies at a young age. They also identify several avenues for further research, including the ways in which boys may feel pressure to display gender congruent characteristics and how this is related to their development.