Purpose. The aim of this study was to investigate the effects of training and triathlon competition on anthropometry, plas-matic free fatty acids (FFA) and hydration status. Methods. Twelve male triathletes were submitted to a 12-week training program to compete in the "32° Pirassununga Half Ironman". Anthropometric measurements such as skinfold thickness and bioelectrical impedance (BIA) as well as urine and blood samples were collected at three intervals: at the beginning of the training program (M-1), before (M-2) and after competition (M-3). FFA were analyzed using a NEFA-C kit. Urine pH and den-sity was determined using reagent tapes and a manual refractometer. Data were analyzed using one-way ANOVA and the Tukey-Kramer post-test (p < 0.05). Results. No differences were found for body mass (M-1 = 71.83, M-2 = 74.22, M-3 = 72.15 kg), percent body fat using skinfolds (M-1 = 10.98, M-2 = 10.92, M-3 = 10.40%), urine density (M-1 = 1.02, M-2 = 1.01, M-3 = 1.02) and urine pH (M-1 = 6.00, M-2 = 5.92, M-3 = 5.35). For BIA and FFA, differences were found after competition (BIA: M-1 = 13.54, M-2 = 13.91, M-3 = 9.45%; FFA: M-1 = 0.16, M-2 = 0.15, M-3 = 1.69 mEq/L). Conclusions. These results illustrate the effects of training and competition on body composition and FFA mobilization. Additionally, after five hours of effort, no evidence of dehydration was found after the race.