This study (1) compared the overall levels of aggressive behaveiour and bullying others and (2) investigated the predictive power of two underlying motives - reactive aggression and the need for peer acceptance and affiliation - between non-immigrant and immigrant youth living in two European countries. In Austria, data on aggressive behaviour was available for analyses, while in Norway bullying others, a subcategory of aggressive behaviour was investigated. The sample comprised 302 non-immigrant Norwegians (48.7% girls), 161 first generation immigrant adolescents living in Norway (51.6% girls), 339 non-immigrant Austrians (51.6% girls), and 126 first generation immigrants (48.4% girls) living in Austria aged 14 to 16 years. Immigrant status was associated with higher levels of bullying others in Norway. In Austria, no differences regarding aggressive behaviour were found. In both countries, multiple group structural equation models revealed that the need for peer acceptance and affiliation - but not reactive aggression - was a predictor of bullying others and aggressive behaviour among immigrants, but not among non-immigrants. Results are discussed regarding the process of acculturation among immigrant youth living in two European countries.