Investigating the adoption and use of the host language is one common method for studying acculturation among immigrants. What is less known is how this type of acculturation changes over time and how individual patterns of change can affect other adaptation processes in the host country, for example within families. This study investigated immigrant adolescents' host language use by applying two recently introduced concepts of acculturative change, pace (the speed in which one acculturates) and relative timing (one's acculturation level relative to coethnic peer acculturation levels), and its relation with family interactions (child disclosure, acculturation-related family hassles). Data comprised a three-wave longitudinal sample of 378 ethnic German immigrant parent-adolescent dyads from former Soviet Union in Germany (adolescent M[subscript age] = 15.7, 62% girls). Latent True-Change models were used to model pace of acculturative changes between waves. Structural equation analyses revealed that acculturative pace in language use predicted family interactions over time: Pace between Wave 1 and 2 predicted higher levels of child disclosure, pace between Wave 2 and 3 increased acculturation-related family hassles. Associations were stronger among recently immigrated families. Relative timing was not related to family interactions at all. The results highlight that understanding the dynamics in immigrant adolescents' acculturation can explain differences in family functioning. Thus, insights into individual acculturative change trajectories have the potential to broaden current knowledge about immigrants' adaptation processes in general.