This study describes the occurrence of reproductive changes in a mullet (Mugil curema) from the Babibtonga Bay, Santa Catarina. Gross and microscopic findings indicated changes in the reproductive system that were characterized by the presence of both male and female gonads, nearing sexual maturity, which was compatible with the diagnosis of intersex. It was not possible to identify predisposing factors that may have contributed to the development of this condition. However, as this species of fish may have their reproductive development affected by anthropogenic influence, it is important to permanently monitor this kind of environment. Considering the number of fish belonging to this species that was examined (n=433), the estimated prevalence for intersexuality was 0.23% (confidence interval: 0.00 to 0.68%, with confidence level of 95%). The findings in this study support the diagnosis of intersexuality in M. curema from the Babitonga Bay, which is the first documented case of this condition in this species on the coast of Santa Catarina, Brazil.