Semen cryopreservation is a technique widely used in commercial and conservation fish farms. However, the success of the technique will depend on the diluent and cryoprotectant solutions added to the semen prior to the freezing procedure.To evaluate the effects of different doses of melatonin on motility, morphology and fertilization capacity of cryopreserved semen of Prochilodus lineatus.Semen was diluted in cryoprotectant solution with added melatonin, resulting in three treatments. A Control Solution (DMSO8% + BTS5%), was compared with T1, T2 and T3 treatments: BTS (5%) + DMSO (8%) plus concentrations of 1, 2 and 3 mM of melatonin, respectively. The diluted semen was frozen in a cylinder of vapour nitrogen and stored at -190°C. The straws were thawed in a water bath at 40°C for 12 s for analysis of sperm motility and morphology, and for evaluation of fertilization rate. The data were submitted to ANOVA, and the means were compared by the Tukey test.There was no statistical difference (P>0.05) between the progressive motility rates and the velocities of the cryopreserved semen in the different treatments. The total motility rate was higher (P 0.05).The addition of melatonin on the cryoprotectant solution did not promote changes on motility, morphology and fertilization capacity of cryopreserved semen of Prochilodus lineatus.