To investigate the diagnostic rate of autism spectrum disorder (ASD) in a high-survival cohort of very preterm children, 77 infants born very preterm (<32 weeks of gestation) were assessed at age 4–6 years old using the Autism Diagnostic Observation Schedule, 2nd edition (ADOS-2), and the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5). Sixteen children (20.8%) were classified as both DSM-5-positive ASD and ADOS-2-identified “autism” which was defined as confirmed ASD in this study. Our result suggests that the prevalence of ASD in very preterm children might be much higher than reported in previous studies when all children were individually evaluated. Further studies in a large sample are required to clarify the true risk of ASD in preterm birth.