Our work use the WGS data present the molecular genetic evidence for a novel mutation potentially underlying autosomal dwarfism in chicken. The identification of the adw mutation provides the basis for future studies towards dwarf status in different species, as well as the functional role of TMEM263 in growth and developmental pathways. Autosomal dwarfism (adw) in chicken is known as a growth deficiency caused by a recessive mutation. The features of autosomal dwarfism are known as a proportionally 30% growth reduction with short shank length. The adw variant was first recognized in the Cornell K-strain of White Leghorns but the genetic causal variant remained unknown. To detect the underlying causal variant underlying the trait of adw, fine mapping was conducted based on previous linkage research on chromosome 1. We found a nonsense mutation in the transmembrane protein 263 gene (TMEM263) that is completely associated with the autosomal dwarf phenotype. Variants were detected by comparing whole-genome sequencing data from white leghorns vs adw chicken. Many potential variants were identified but after filtering for the known variant with variant databases, only one potential variant remained associated with autosomal dwarfism. A stop gain variant in TMEM263 is found unique in dwarf chicken and absent in normal-sized controls. In human, TMEM263 is associated with bone mineral density and the protein interacts with growth hormone 1. Therefore the nonsense mutation in TMEM263 likely leads to a protein truncation and therefore affects its function.