The aim of this study was to estimate the environmental effects and genetic parameters on carcass traits (carcass weight, eye muscle area, backfat thickness and marbling score) of 8,027 commercial Hanwoo steers. The data was collected from 458 individual farms for 2007 to 2015 in Jeongeup area of Jeonbuk province. Environmental effects were subjected to ANOVA and genetic parameters were estimated using a multiple trait animal model and average information restricted maximum likelihood (AIREML) procedures. Mean and standard deviation for the CW, EMA, BFT and MS were 444.00±45.11 kg, 96.26±11.64 cm2, 15.35±5.47 mm and 6.88±1.84 score, respectively with carcass traits significantly affected (p<0.001) by slaughtered year, season and location. Estimated heritabilities for CW, EMA, BFT and MS were 0.52, 0.39, 0.39 and 0.47, respectively. Genetic correlation of CW with EMA, BFT and MS were estimated to be 0.42, 0.38 and 0.17, respectively. Genetic correlation of EMA with BFT and MS were estimated to be –0.03 and 0.41, respectively. Genetic correlation of BFT and MS were –0.02. These results could be useful as basic data for the improvement of Hanwoo in commercial farms.