Background and purpose: Separation anxiety and social anxiety are common forms of anxiety in school-age children and are closely related to affective disorders in adulthood. Investigations of the factors associated with these symptoms and their mechanisms are critical for interventions. Trait anger and anger expression of two components of anger have important associations with externalizing behaviors; however, their relationships with internalizing symptoms remain largely unexamined. The aims of this study were to examine the direct relationship between children’s frustration and aggression and their separation anxiety and social anxiety, respec-tively. The moderating effect of children’s verbal ability on the relationships among frustration, aggression, and symptoms of separation and social anxiety were also investigated. Methods: This study recruited seventy-one typically developing chil-dren attending elementary schools in northern Taiwan (mean age 9.24 years; 45 boys) and their parents. Parents completed demographic information, and children self-reported their frustration (i.e. trait anger), aggression (i.e. anger expression), separation anxiety, and social anxiety symptoms on inventories. Children’s verbal abilities were assessed with the Wechsler Intelligence Scale for Children, Fourth Edition. Results: Frustration positively correlated with symptoms of separation anxiety and social anxiety; however, only frustration had a significant predicting effect on separation anxiety after controlling for gender and age. Aggression had no significant correlations with separation or social anxiety; however, verbal ability moderated the relationship between aggression and social anxiety. Conclusions: Frustration increases the risk of separation anxiety in school-age children. The asso-ciation between aggressive behavior and social anxiety symptoms depends on the level of children’s verbal ability.