Background. Cri du chat syndrome (CdCS) is a rare orphan genetic disorder. Infants with CdCS have a neurodevelopmental dysfunction, but there are limited studies on their spontaneous movements or effect of the early interventions in children with CdCS. This study aimed to describe early spontaneous movements and investigate the effects of an early intervention in an infant with the CdCS. Case. We analyzed the detailed general movements assessment (GMA) of an infant with CdCS at 14 weeks, and the Bayley Scales of Infant and Toddler Development-third edition (Bayley-III) were used for the determining and the follow-up of developmental functioning at 14 weeks, 6 months and 12 months. The infant was included in an early intervention beginning from 14 weeks. Fidgety movements were absent. The motor repertoire appeared significantly reduced, and the movement character was monotonous at 14 weeks. Although the infant achieved some developmental milestones with the early intervention program, the improvements were not reflected in the Bayley-III composite score. Conclusions. As a consequence, abnormal GMA results, including fidgety movements and concurrent movement patterns, seen in CdCS can be associated with early signs of neurodevelopmental dysfunction. Early intervention programs in infants with genetic disorders could help enable the early achievement of motor milestones.