Deficits in language skills are a risk factor for later aggressive behaviour. However, previous research has mainly addressed clinical or high-risk samples and relations between language and aggressive behaviour in preschoolers and children in primary school. Based on a German longitudinal project with N = 547 typically developing children, the present study investigated whether the effects of young children's language skills on their aggressive behaviour and their hostile intent attribution (HIA) can still be observed in adolescence. Path models showed that language at age 3 predicted aggressive behaviour (measured with self-ratings of various facets of aggression) and HIA (assessed with the Intent Attributions and Feelings of Distress Measure adopted from) over a 10-year period, while controlling for important child and family characteristics and initial levels of aggressive behaviour at age 3. Moreover, the predictive impact of early language on aggressive behaviour was mediated by HIA but not by parental ratings of their children's positive peer relations with classmates at age 7. Implications and directions for future research are proposed.