For individuals with autism spectrum disorder (ASD), early and accurate diagnosis enables early intervention, which leads to improved quality of life. The diagnostic label of ASD has only been recognized in Vietnam since 2000 and the number of children who have been diagnosed has increased dramatically. However, there is limited understanding about the condition. This article aims to describe the current assessment and diagnostic practices in Hanoi, Vietnam, a low resource setting. Data for this article came from in-depth interviews with parents of children with ASD and service providers, and observation at health clinics and early intervention centers that provide ASD assessment during field work from July 2011 to May 2012. This study reveals that although there is some improvement in assessment services, parents still face a number of challenges in accessing quality assessment and diagnosis of ASD in Vietnam. These include rushed and perfunctory assessment; a lack of clinical guidelines for assessment; limited communication among health professionals in assessment teams, and between professionals and parents of children with ASD. Public awareness-raising of the signs of autism, capacity building for professionals, development of practical and contextual appropriate assessment protocols are needed to enhance the accessibility and quality of assessment services.