Polymorphisms evaluated in this study are registered in the Single Nucleotide Database (dbSNP) of the National Center of Biotechnology Information (NCBI). The objective of this study was to determine the association of polymorphisms in the growth hormone (GH NCBI dbSNP rs41923484 and rs134687399), somatostatin (SST rs17870997), growth hormone releasing hormone (GHRH rs380969504), myostatin (GDF8 rs383271508 and rs137528458) and leptin (LEP rs29004487, rs29004488 and rs29004508) genes with growth and carcass traits. To better comprehend the association between the aforementioned polymorphisms and growth, serial measurements of body weight, withers height, chest girth and abdominal girth at 9, 14, 20 and 28 months of age were taken in Japanese Black steers that were under progeny test from 2005 to 2013 (n = 280) at the Livestock Improvement Association of Miyazaki. Carcass measurements were taken and their association with genetic polymorphisms was evaluated. An ANOVA was done and post hoc analysis was done using Tukey-Kramer’s honestly significant test. Polymorphisms in the GH, GHRH, GDF8 (rs137528458) and LEP (rs29004508) were significantly associated (p < 0.05) with some growth and carcass traits. Thus, these polymorphisms might be useful markers for the improvement of growth and carcass traits in Japanese Black cattle.