To define the clinical characteristics of patients with variants in TCF20, we describe 27 patients, 26 of whom were identified via exome sequencing. We compare detailed clinical data with 17 previously reported patients.Patients were ascertained through molecular testing laboratories performing exome sequencing (and other testing) with orthogonal confirmation; collaborating referring clinicians provided detailed clinical information.The cohort of 27 patients all had novel variants, and ranged in age from 2 to 68 years. All had developmental delay/intellectual disability. Autism spectrum disorders/autistic features were reported in 69%, attention disorders or hyperactivity in 67%, craniofacial features (no recognizable facial gestalt) in 67%, structural brain anomalies in 24%, and seizures in 12%. Additional features affecting various organ systems were described in 93%. In a majority of patients, we did not observe previously reported findings of postnatal overgrowth or craniosynostosis, in comparison with earlier reports.We provide valuable data regarding the prognosis and clinical manifestations of patients with variants in TCF20.