The early assessment of autism spectrum disorders (ASDs) is important to improving patient outcomes, allowing family members to prepare for and cope with symptoms, and assisting in plans for appropriate educational opportunities. However, little is known about factors that influence the time lag between the parents' first concerns and the first visit to a hospital that offers child psychiatric service. We investigated factors associated with the time lag between the first parental concern and the first visit to a hospital that offers child psychiatric services, among children in Japan with ASDs. A questionnaire was distributed to caregivers of ASD children, through child psychiatrists who work at 16 leading hospitals in child psychiatric services in Japan (N = 1513). We found that a younger child age, a caregiver's lack of knowledge of whom to consult when first concerned about symptoms, and the typically indirect means of attaining services (especially without a referral) each heightened the odds of there being a longer time lag. Visiting another institution, and then going to a hospital that offers child psychiatric services without a referral, was a typical scenario that often led to such time lags. A national health policy to facilitate a referral system that coordinates hospitals that offer child psychiatric services with other medical institutions, the health sector, the welfare sector, and educational institutions is needed, to promote the timely provision of child psychiatric services. (Contains 4 tables.)