This article investigates long‐term effects of the timing of language course participation among immigrants, focusing on self‐assessed immigration country language skills and interethnic social contacts among immigrants from Turkey and Morocco who came to Western Europe mainly during the guest worker period. Data stem from the 2008 Six Country Immigrant Integration Comparative Survey. We find a positive, long‐term impact of course participation in the first four years after immigration on language skills and social contacts. Results support linguistic theories on the benefits of early language instruction and sociopsychological theories on long‐term effects of (even short) social belonging interventions on participants' perseverance in achieving educational success.