Prader-Willi syndrome (PWS) is a rare neurodevelopmental disorder caused by a deletion in the 15q11-q13 region. This study aimed to examine the effect of sensory integration-based occupational therapy on sensory processing, gross motor skills, behavior, and feeding in a child with PWS. A four-year-old child with PWS underwent sensory integration-based occupational therapy for 48 weeks, with two 40-minute sessions per week. Evaluations using Dunn Sensory Profile, Gross Motor Function Measurement, Child Behavior Rating Scale, and Pediatric Feeding Assessment were done before intervention and at the 16th, 32nd, and 48th weeks. Positive improvements in sensory processing, motor skills, behavior, and feeding were observed at each follow-up compared to the previous one. Evaluation of developmental areas and application of sensory integration-based occupational therapy in a child with PWS is an effective approach to support the child's development.