Social and emotional learning (SEL) is inherently relational, shaped by the interactions children have within their homes, schools, and communities. Grounded in ecological systems theory, this chapter explores how family-school-community partnerships can serve as a powerful mechanism for promoting SEL and fostering positive developmental outcomes. Research consistently demonstrates that collaborative relationships among families, schools, and community members enhance children's academic, social-emotional, and behavioral well-being. This chapter reviews empirical support for these partnerships, highlighting their role in advancing equity, cultural responsiveness, and strengths-based approaches to education. Further, we discuss implementation science strategies to better integrate family-school-community partnerships into SEL programs. Finally, we provide evidence-based practices to support meaningful cross-system collaboration, offering actionable recommendations for educators, families, and policymakers seeking to create environments that nurture children's SEL across multiple contexts. [This chapter was published in: "Handbook of Social and Emotional Leaning, 2nd Edition," Guliford Press, 2024, pp. 115-128.]