Mowat-Wilson syndrome (MWS) is characterized by severe mental retardation with seizures, specific facial dysmorphism, Hirschsprung disease, anomalies of the corpus callosum, and genitourinary and cardiac malformations. The cause of MWS is a de novo mutation in the ZEB2 gene. This report describes a Turkish boy who was clinically diagnosed with MWS and had his diagnosis confirmed by molecular analysis of the ZEB2 gene. The investigation identified a heterozygous complex rearrangement in exon 8 of ZEB2, specifically a 48-nucleotide deletion and a 44-nucleotide insertion that caused a frameshift. MWS is a relatively newly identified disorder, and even MWS patients without Hirschsprung disease can be diagnosed easily based on clinical findings alone.