Children with autism spectrum disorder (ASD) are reported to have greater levels of anger rumination than typically developing children. This study examined anger rumination in children with ASD in comparison to children with disruptive behavior disorder without ASD. We also tested if anger rumination is associated with aggression and the core ASD symptoms of restricted and repetitive behaviors (RRBs). This study included three groups of children aged 8–16 years: 63 had ASD (ASD group), 79 had disruptive behavior disorder (DB group), and 40 healthy controls (HC). ASD and DB groups showed greater anger rumination relative to the HC group. Anger rumination was associated with RRBs in children with ASD, suggesting the link to core ASD symptoms.