Purpose <p>Whilst the survival rate of preterm (PT) children has increased significantly, the number of neurodevelopmental problems and behavioural difficulties throughout the lifespan has also risen, especially in those born very or extremely PT. These vulnerabilities can lead to certain psychopathologies, though there is also evidence for a specific subclinical and more subtle behavioural pattern in PTs. Our aim is to pinpoint important vulnerabilities of PT children and to further investigate this “preterm behavioural phenotype”.</p> Methods <p>We investigated a group of thirty-nine school-aged very and extremely PT children without major neurological impairments or a formal autism diagnosis, and we compared them to a cohort of thirty-eight age- and sex-matched full-term (FT) controls. Autism-related difficulties in social functioning and repetitive behaviours, as well as behavioural problems, anxiety, and attachment, were assessed through self-reports from the child and/or informant reports from the parent(s) and clinicians, with informant sources varying across assessments.</p> Results <p>Compared to FT peers, PT children displayed significantly increased anxiety, attention problems and autism-related social difficulties. No significant group differences were evident in terms of autism-related restricted/repetitive behaviours or self-reports of peer and parental attachment.</p> Conclusion <p>Even in a PT population without major neurological impairments or a clinical diagnosis of autism, important clinical-behavioural differences were evident in line with a preterm behavioural phenotype. Thus, delineating this subclinical PT pattern can be of relevance to recognize and validate meaningful difficulties experienced by these children that fail to reach the clinical threshold but could still benefit from certain interventions.</p>