The goal of the present study was to investigate the relationship between parental acculturation attitudes and second language (L2) skills and acquisition in immigrant children and to identify the mechanisms that potentially mediate between parental acculturation attitudes and children's L2 skills and acquisition. Our longitudinal study is based on a sample of 252 children with German as L2 (age t[subscript 1]: M = 41 months; t[subscript 2]: M = 57 months) and their parents. Research Findings: Results revealed that parental acculturation attitudes toward the country of origin negatively correlated with children's L2 skills at t[subscript 1] and at t[subscript 2]. Furthermore, time spent in early childcare predicted L2 skills at t[subscript 1] and at t[subscript 2]. Parental L2 proficiency and children's contact with German language speakers outside of childcare were related to children's L2 skills at t[subscript 1]. Parental L2 proficiency mediated the relationship between parental acculturation attitudes and children's L2 skills. Practice or Policy: The findings support the importance of early childcare attendance and parental acculturation for L2 skills and acquisition in children with an immigrant background.