Aim: To characterize the changes in body composition, mood state and cardiac autonomic modulation in Brazilian Jiu-Jitsu (BJJ) of athletes in the pre- and post-competitive periods. Methods: Eight male athletes were evaluated in 3 moments: 14 days and 1 day before the fight, and 2 days after the competition. Evaluations of body composition, mood state, and cardiac autonomic modulation were performed. The repeated measures Anova test, Pearson and Spearman correlation were used for data analysis (p < 0.05). Results: We observed reductions in anger (6.80 ± 1.69 vs. 4.20 ± 1.67 vs. 3.40 ± 1.07) and tension (6.60 ± 0.81 vs. 5.40 ± 0.75 vs. 2.60 ± 0.88) after competition. Vigor was reduced one day before the competition and remained the same two days after the competition (12.80 ± 1.60 vs. 10.00 ± 1.95 vs. 10.40 ± 1.03). In addition, there was an increase in sympathetic modulation (LF-PI: 2942 ± 655.3 vs. 5479 ± 2035 vs. 5334 ± 2418 abs). There was a positive correlation between the state of vigor and sympathetic modulation (r = 0.55), a negative correlation between the states of depression and sympathetic modulation (r = -0.68) and confusion and sympathetic modulation (r = -0.67). Conclusion: These findings raised concerns about the preparation of these athletes for competitions since changes in the state of vigor might reduce performance and increase cardiovascular risk.