It is well-recognized that measurement options for diagnosing and monitoring children with neurogenetic syndromes (NGS) associated with moderate to severe intellectual impairment are limited (Berry-Kravis, Dev Med Child Neurol 10.1111/dmcn.13018, 2016), and caregivers experience significant concerns regarding the assessment process. However to date, these concerns have not been summarized into actionable steps for clinicians and test-makers. As such, we used a mixed methods approach to assess caregiver-derived perceptions and suggestions for improving assessments in NGS. Results indicated many shared challenges and suggestions for improvement, particularly in the domains of testing procedures and examiner communication. Integrating these suggestions into future protocols is an important next step toward improving the quality of assessment procedures for children with NGS and their families across both clinical and research contexts.