BACKGROUND: Coffin-Siris syndrome is a rare genetic disease with heterozygous variants in the ARID1A, ARID1B, ARID2, DPF2, SMARCA4, SMARCB1, SMARCE1 or SOX11 genes. It may manifest with somatic anomalies, deafness, urogenital malformations, recurrent infections, mental retardation, speech deficit, agenesis of the corpus callosum, convulsions, hypotonia, developmental delay, and scoliosis. CASE REPORT: A 14-year-old boy with Coffin-Siris syndrome due to variants in the ARID1A gene was referred to the clinic. His rehabilitation over a 9-year period was described. The problem of assessment and the approach to rehabilitation was discussed, enabling a progressive remodelling of the cognitive-behavioural disorders that most hindered the possibility of his acquiring new skills and achieving social and family integration. CLINICAL REHABILITATION: A protracted, customised, multiprofessional rehabilitation approach, centred on realistic functional objectives, implemented with the direct involvement of the family and school, was the only way to achieve the maximum independence and social and family integration permitted by his residual disability.