Young children in immigrant families tend to face more challenges and can often call upon fewer resources than their native-born peers. This situation adversely affects their social–emotional development. In this study, the development of emotion knowledge of 576 immigrant and native-born German children, aged 3–6 years, was compared at three time points over a 12-month period by means of a latent growth curve analysis. Language abilities and behavioural self-regulation were examined as mediators of the relation between immigration background and emotion knowledge. The immigrant children showed less emotion knowledge than did their native-born peers at each point of measurement. These effects were partially mediated by their behavioural self-regulation and their language abilities. How behavioural self-regulation and language abilities affect the development of emotion knowledge and what this effect means for interventions are discussed.