Studies comparing mathematical abilities of children with autism spectrum disorder (ASD) and typically developing children are hitherto scarce, inconclusive, and mainly focusing on elementary school children or adolescents. The present study wants to gain insight into the foundation of mathematics by looking at preschool performances. Five early numerical competencies known to be important for mathematical development were examined: verbal subitizing, counting, magnitude comparison, estimation, and arithmetic operations. These competencies were studied in 20 high-functioning children with ASD and 20 age-matched control children aged 4 and 5 years. Our data revealed similar early number processing in children with and without ASD at preschool age, meaning that both groups did not differ on the foundation of mathematics development. Given the pervasiveness and the family impact of the condition of ASD, this is an important positive message for parents and preschool teachers. Implications and several directions for future research are proposed.