The current study examined whether social competence and autistic traits are related to anxiety and depression in autistic and non-autistic children. Parents of 340 children aged 6 to 12 years old, including 186 autistic and 154 non-autistic children completed the Autism Spectrum Quotient (AQ) to assess their child's autistic traits, the Multidimensional Social Competence Scale (MSCS) to assess their child's social competence, and the Behaviour Assessment Scale for Children 2 (BASC-2) to assess their child's internalizing symptoms of depression and anxiety, and children were administered the Wechsler Abbreviated Scale of Intelligence, Second Edition (WASI-II) to assess their intellectual abilities. Hierarchical multiple regression analyses were conducted to investigate the relations between social competence, autistic traits, anxiety, and depression. Social competence was related to anxiety and depression symptoms in autistic children, but only depression symptoms in non-autistic children, above and beyond the effects of autistic traits, IQ and age. Autistic children were also reported to experience more severe anxiety and depression symptoms, and more autistic traits were related to higher levels of anxiety and depression in both groups. These findings suggest that social competence and internalizing symptoms are intricately connected in autistic children and need to be jointly considered in both assessment and intervention. The social implications are discussed with an emphasis on acceptance of diverse social styles as a viable avenue to reduce children's internalizing symptoms.