AbstractResearch examining the behavioural and psychological functioning of children and adults with sagittal synostosis (SS) is scarce, often disparate, and lacks well-matched control groups. Clinicians are therefore often unable to provide families with guidance about their child’s anticipated functioning. Social media channels were used to recruit community-based parents of children with SS, or adults with SS (n = 56) and an age- and sex-matched control group (n = 56). Families completed an online survey encompassing a range of demographic and clinical variables and a comprehensive battery of validated questionnaires. Surveys were either parent-rated (children 2 to < 5 years), both parent-rated and self-reported (children 5 to ≤ 18 years), or self-reported only (adults ≥ 19 years). Results show that for both unadjusted and adjusted (SES) analyses, children and adults were functioning at a similar level to their peers. Whilst mean parent-rated scores generally indicated that children with SS were experiencing slightly more difficulties, group differences were not statistically significant. Most adjusted Hedges’ g effect sizes were trivial (g = .10) to small (g = .20). Nonetheless, more children with SS were assessed as having clinically significant problems on each composite of the Behavior Assessment System for Children 3^rd Ed. In addition, screening rates of Attention Deficit Hyperactivity Disorder (18%; Behavior Rating Inventory of Executive Function 2) and Autism Spectrum Disorder (15%; Social Responsiveness Scale-2), in children with SS, were high. Findings suggest that children with SS should be monitored and referrals for appropriate support made readily available, as required.