Williams syndrome is a rare congenital syndrome with distinctive craniofacial features, cardiovascular abnormalities, and behavior characteristics including mental retardation. The dental abnormalities have received scant attention in previous literature. The aim of this study was to describe dental characteristics in individuals with Williams syndrome. In a group of 41 individuals more than 10 years of age, 40.5% had agenesis of one or more permanent teeth and 11.9% had agenesis of 6 permanent teeth or more. The mesio-distal and labio-lingual dimensions of permanent tooth crowns were measured on 31 dental study casts from individuals older than 12 years. The mesio-distal and labio-lingual dimensions were significantly smaller compared with a reference sample. An analysis of tooth morphology was performed on the same dental study casts revealing altered tooth morphology. A high proportion of maxillary and mandibular incisors was tapered or screwdriver shaped. An evaluation of taurodontism on mandibular permanent molars was performed using a metric crown-body/root ratio. However, most of the molars rated as being taurodontic had short or extremely short total tooth lengths and could thus be rated taurodontic without meeting the classical definition. The results of this study indicate that although there is variation in dental development in individuals with Williams syndrome, agenesis of permanent teeth in combination with aberrations in tooth size and morphology may affect dental esthetics and complicate orthodontic and prosthodontic treatment.