Sudden cardiac death in the young (SCDY) is a devastating event that often has an underlying genetic basis. Manchester Terrier dogs offer a naturally occurring model of SCDY, with sudden death of puppies as the manifestation of an inherited dilated cardiomyopathy (DCM). We performed a genome-wide association study for SCDY/DCM in Manchester Terrier dogs and identified a susceptibility locus harboring the cardiac ATP-sensitive potassium channel geneABCC9. Sanger sequencing revealed anABCC9p.R1186Q variant present in a homozygous state in all SCDY/DCM-affected dogs (n= 26). None of the controls genotyped (n= 398) were homozygous for the variant, but 69 were heterozygous carriers, consistent with autosomal recessive inheritance with complete penetrance (p= 4 × 10−42for the association of homozygosity forABCC9p.R1186Q with SCDY/DCM). This variant exists at low frequency in human populations (rs776973456) with clinical significance previously deemed uncertain. The results of this study further the evidence thatABCC9is a susceptibility gene for SCDY/DCM and highlight the potential application of dog models to predict the clinical significance of human variants.