Chiari malformations are multifactorial and heterogeneous entities, characterized by abnormalities in the posterior fossa. They have been identified in association with various genetic syndromes in recent years. Two previous studies have noted an association of Chiari malformations with Rubinstein–Taybi syndrome (RTS). In this clinical report, we highlight identical twins with RTS caused by a mutation in CREBBP that presented with slightly different Chiari malformations in association with an extensive multiloculated syrinx and scoliosis. RTS has been found to be associated with craniocervical abnormalities in literature review, and this clinical report demonstrates the prudent consideration of the physician who cares for patients impacted by RTS to effectively screen via symptomatology and physical examination for Chiari pathology or other craniocervical abnormalities. © 2011 Wiley Periodicals, Inc.