In the current study, we test the precursors to the Dark Triad traits, as well as the role that the Dark Triad traits have on predicting aggression. Participants (N=599, age range=18–83years) completed measures of the Dark Triad traits, emerging adulthood facets, and reactive and proactive aggression. In support of our theoretical model, (a) participant's age was related to all emerging adulthood facets except other and self-focused, (b) aggression was predicted by all the Dark Triad traits, and (c) several emerging adult facets predicted various Dark Triad traits. These findings were further substantiated by mediation tests that confirmed our theoretically derived adult developmental pathways from participant age to aggression. Specifically, results showed that feeling in-between, negativity, and identity exploration were the key emerging adult variables that served as mediators from age to aggressive behavior by predicting at least one Dark Triad trait(s). Overall, the Dark Triad traits are an important precursor to aggressive behavior, but also likely develop as a function of adult developmentally relevant predictors. •Tested the relations between Dark Triad, emerging adulthood, age, and aggression.•Dark Triad traits positively predicted aggression.•Certain emerging adulthood facets predicted Dark Triad.•Age predicted emerging adulthood facets.•Multiple mediated pathways between age and aggression were observed.