Congenital heart defects (CHDs), a wide variety of developmental abnormalities in the structures of the heart and the great thoracic blood vessels, are the most common form of birth defect in humans worldwide. CHDs are accountable for substantial morbidity and are still the leading cause of birth defect‑related deaths. Recent studies have demonstrated the pivotal roles of genetic defects in the pathogenesis of CHDs, and a great number of genetic mutations have been associated with CHDs. Nevertheless, CHDs are a genetically heterogeneous disorder and the genetic basis underlying CHDs in an overwhelming majority of cases remains unclear. In the present study, the coding exons and flanking introns of the heart and neural crest derivatives expressed transcript 1 (HAND1) gene, which encodes a basic helix‑loop‑helix transcription factor crucial for cardiovascular development, were sequenced in 158 unrelated patients with CHDs, and a de novo heterozygous mutation, p.K132X, was identified in a patient with double outlet right ventricle (DORV), as well as ventricular septal defect. The nonsense mutation, which was predicted to produce a truncated HAND1 protein lacking 84 carboxyl‑terminal amino acids, was absent in 600 control chromosomes. Functional analyses revealed that the HAND1 K132X mutant had no transcriptional activity. Furthermore, the mutation disrupted the synergistic activation between HAND1 and GATA binding protein 4 (GATA4), another cardiac core transcription factor causally linked to CHDs. To the best of our knowledge, this is the first report on the association of HAND1 loss‑of‑function mutation with an enhanced susceptibility to DORV in humans. These findings expand the phenotypic spectrum linked to HAND1 mutations, suggesting potential implications for the development of novelo prophylactic and therapeutic strategies for DORV.