The aim of the study was to identify polymorphisms within nuclear DNA genes and determine their association with the performance traits of farmed raccoon dogs. The study involved 354 animals and their breeding documentation data. Myostatin (MSTN), insulin-like growth factor 1 (IGF1), and growth hormone (GHR) genes were amplified, sequenced, and subjected to bioinformatics and statistical analysis. Estimation of variance components was performed with the residual maximum likelihood (REML) method, and best linear unbiased prediction (BLUP) of the breeding values was carried out. The predictors of the traits of direct additive, maternal additive, and random-specific maternal environmental effects were analysed. Within the nucleotide sequences of the analysed genes, one silent single nucleotide polymorphism (SNP) was identified in exon 1 of the MSTN gene. The analysis of the variance of the fixed-specific maternal environmental effect revealed statistically significant differences in the body weight among raccoon dogs with alternative polymorphisms. The mean effects of the estimators of polymorphism addition and dominance measured by MSTN gene regression had mostly a significant impact on the level of the traits estimated in animals. There was statistically significant association of the polymorphism in the MSTN gene with the body weight in raccoon dogs, which validates selection thereof as a candidate gene for this economically most important performance trait of raccoon dogs.