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This work aimed to use the biometric measurements of steers in the rearing phase to predict the carcass characteristics of Nellore cattle managed in tropical pastures. Data from 60 young bulls in the rearing phase supplemented and managed on Brachiaria brizantha pastures during the rainy season and dry-rainy transition and slaughtered at 24 months old after 112 days in feedlot. Descriptive statistical analyses and Pearson's correlation coefficients were performed. The goodness of fit of the developed equations was evaluated by the coefficients of determination (R2) and square root mean error (RMSE). The average body weight (BW) in the rearing phase was 295 kg BW corresponding to 72.8 kg BW0.75. The average of the loin eye area (LEA), subcutaneous fat thickness (SFT), and rump fat thickness (RFT) measured by ultrasound were 43.5 cm2, 3.3 mm, and 3.6 mm, respectively. The correlation between BW and BW0.75, and LEA were positively significant. Total weight gain (TWG) and average daily gain (ADG) showed a correlation of 0.4216 and 0.4235 with SFT. To LEA prediction, the best fitting considered BW, TWG, and average daily gain (ADG) variables. Whereas SFT, considered BW, and ADG, and to RFT prediction, the best fitting considered only BW. The internal validation (k = 10) of the equations for predicting observed random error of 98.74% in LEA equation, 71.35% in SFT equation, and 98.59% in RFT equation. Body weight and weight gain during the rearing period can be used as predictor variables for LEA, SFT, and RFT of Nellore cattle kept in tropical pastures. [ABSTRACT FROM AUTHOR]