Autism spectrum disorder is a developmental disorder that includes deficits in social communication and interaction, and restricted and repetitive behaviours, interests, or activities. This survey was done to assess autism spectrum disorder prevalence in 16- to 30-month-old children at an urban-rural distribution and determine the association of socioeconomic and demographic conditions. An observational cross-sectional study was conducted in 30 districts of Bangladesh. Three-stage cluster sampling was used with 'Red Flag', Modified Checklist for Toddlers and "Diagnostic and Statistical Manual of Mental Disorders, 5th Edition," respectively. Data editing and analysis were done using CSPro 6 and SPSS 23. The survey included 37,982 households (71% rural, 29% urban) with 38,440 children. 'Red Flag' was positive in 209/10,000 children. Modified Checklist for Toddlers was positive in 149/10,000 children. "Diagnostic and Statistical Manual of Mental Disorders, 5th Edition"--positive autism spectrum disorder prevalence was 17/10,000 young children (boys 24/10,000, girls 9.8/10,000). Prevalence was higher in urban than rural (25/10,000 and 14/10,000 respectively). It was 77/10,000 in mothers aged 35-39 years and 23/10,000 in children of fathers aged 40 years. For families within the lowest wealth quintile, the autism spectrum disorder prevalence was 15/10,000. Autism spectrum disorder at very young ages in Bangladesh is still low. It was higher in urban areas, with the advanced age of parents, especially mothers, and in families with higher wealth quintiles.