Homophobic-name-calling and aggression in adolescence is linked to the policing of masculinity. Although the definition of masculinity changes as society changes, one thing which has remained constant across time is the need to prove it, often through enactments of homophobia and homophobic aggression. Chapter one outlines the wider societal context, background literature and rationale for this thesis. Chapter two presents the systematic review and meta-analysis which explores the relationship between masculinity and homophobic-name-calling in adolescents. This paper is the first to review this relationship quantitively, with a meta-analysis revealing a statistically significant relationship between masculinity and homophobic-name-calling. This review sheds light on the role of homophobic-name-calling as a mechanism for enforcing masculinity within friendship groups. Additionally, the narrative synthesis in this review identifies empathy as a potential protective factor against homophobic-name-calling. Chapter three, an empirical study, proposes a new model for understanding masculinity, equating its functioning to that of narcissism, and explores how this leads to homophobic aggression in adolescents. Participants included 226 young people between the ages of 12 and 19 from one United Kingdom (UK) secondary school and this study adopted a quantitative methodology. Multiple linear regression, mediation and moderation analysis led to a final path model which illustrated the mechanisms behind homophobic aggression for the boys in this sample. Findings suggest that empathy plays an important role in the relationship between masculinity and homophobic aggression. Findings also add weight to the novel theory that masculinity functions in a similar way to narcissism.