Isodicentric chromosome 15 [idic(15)] is a rare chromosomal abnormality that occurs due to inverted duplication of chromosome 15q. It is associated with many clinical findings such as early central hypotonia, developmental delay, cognitive dysfunction, autism spectrum disorders, and seizure. Delayed development is a common problem referred to pediatric rehabilitation clinics. A 9-month-old boy with delayed development was referred to our clinic for assessment and treatment. On chromosomal analysis, he was diagnosed as idic(15) syndrome with 47,XY,+idic(15)(q12) on karyotyping. Herein we describe his clinical manifestations and provide a brief review of the related literature.