Objective: To investigate the mediating role of family support in family expressiveness and non-only-child adolescents. Methods: 571 non-only-child adolescents were surveyed by Family Expressiveness Questionnaire Short Form, Family Support Inventory and Life Satisfaction Inventory. Results: (1) Positive family expressiveness is positively correlated with family support and life satisfaction of nononly-child adolescents, respectively; while negative family expressiveness is negatively correlated with family support and life satisfaction of non-only-child adolescents; meanwhile, family support and life satisfaction of non-only-child adolescents are positively correlated. (2) Family support mediates the relationship between family expressiveness and life satisfaction of non-only-child adolescents. Specifically, family support plays a completely mediating role between positive family expressiveness and life satisfaction of non-only-child adolescents, and partly mediates between negative family expressiveness and non-only-child adolescent life satisfaction. Conclusion: Family expressiveness, family support, and life satisfaction of non-only-child adolescents are closely related. Family expressiveness with different valence affects the life satisfaction of non-only-child adolescents in different ways.