Bystander intervention has been identified as an effective strategy to resolve bullying incidents. Research suggests that student willingness to intervene (WTI) is a robust predictor of bystander intervention. Toxic masculinity is "the constellation of socially regressive male traits that serve to foster domination, the devaluation of women, homophobia, and wanton violence," (Kupers, 2005, p. 71). Little research has examined how features of toxic masculinity such as attitudes surrounding bullying and sexual harassment, social dominance orientation, and homophobic bullying are related to longitudinal changes in WTI across adolescence. The present study uses growth mixture modeling (GMM) to examine the heterogeneity of WTI among middle school boys and multinomial logistic regression to understand concurrent and distal associations with features of toxic masculinity.