This study aimed to describe the behavioral profile of individuals with SYNGAP1-ID. Parents/carers of 30 individuals aged 3-18 years old with a diagnosis of SYNGAP1-ID and 21 typically developing individuals completed the Vineland-3 Adaptive Behavior Scale and the Child Behavior Checklist. We found that those with SYNGAP1-ID showed fewer adaptive behaviors and higher levels of internalizing and externalizing behaviors across almost all domains compared to typically developing controls. There was some evidence that these differences were greatest in older children, and more apparent in those with co-occurring epilepsy. This characterization of the phenotype of SYNGAP1-ID significantly aids our understanding of the behavioral profile of this population and is a step towards the development of tailored interventions.