This mixed-methods study investigated the impact of parental involvement, social support, and peer relationships on L2 learning motivation among Chinese university students learning English as a foreign language (EFL). Quantitative data from 326 students and qualitative data from semi-structured interviews with 20 students were analyzed. Hierarchical regression analyses revealed that parental involvement significantly predicted all three components of L2 motivation: ideal L2 self, ought-to L2 self, and L2 learning experience. Peer relationships also positively predicted ideal L2 self and L2 learning experience. While social support was not a significant predictor in the quantitative analyses, the analysis of the qualitative data revealed its nuanced role, with students emphasizing the importance of diverse sources of support, including peers, teachers, mentors, and online communities, in fostering a sense of belonging and enhancing motivation. The study highlights the complex interplay of familial and social influences on L2 motivation, offering valuable insights for educators and parents in supporting EFL learners.