The best practice guidelines for assessing and diagnosing Autism spectrum disorder (ASD) in developed countries present a challenge for health practitioners in developing countries where services are very limited. As a starting point to understand these challenges, the present study investigated the needs and practices of urban Indonesian practitioners in their assessment of young children with ASD. A questionnaire was developed and distributed to 67 Indonesian health practitioners who reported that they assessed at least one case of ASD a month. Using descriptive statistics, it was found that best practice components were not easily applied in Indonesia. The use of a multistage system and a multidisciplinary approach remains a challenge. Furthermore, most practitioners endorsed the need for validated tools in Indonesian language and training in assessing ASD. This is the first study, to our knowledge, that aims to evaluate the diagnostic processes, needs and challenges of Indonesian practitioners in diagnosing ASD.