The aim of the present study was to evaluate the influence of probiotics prepared from Bacillus subtilis (strain C-3102-Calsporin®; Calpis, Tokyo, Japan) as a dietary supplement on several reproductive aspects of female ‘matrinxã’(Brycon amazonicus), including hematological parameters, immunological characteristics and total lipid concentrations in muscle and liver tissue. The broodstock were kept in two ponds of 600 m2, at a density of 50 fish per pond, from March to November 2008. The fish were divided into two treatment groups: untreated control fish (T1), and fish fed with 10 g of probiotics per kg of ration (T2). Fish were fed a diet containing 32% crude protein (CP), 7% crude fat (CF), and 6.5% ether extract (EE) twice daily at a rate of 1% of the total biomass per day during the coldest months (May through August) and 3% during the warm season (March, April and September through November). During the reproductive period, 20 individuals from each treatment group were selected for the experiments; two doses of crude carp pituitary extract were given to females in 10-h intervals, and one dose was given to the males at the same time the females were given the second dose. A total of 20 fish were used for the hematological analyses. After anesthetization, blood samples were withdrawn by caudal puncture to determine the total number of cells, differential and total leukocyte counts, thrombocyte count, hematocrit, hemoglobin rate and plasma cortisol and glucose levels. The hematimetric index mean corpuscular volume (VCM) and mean corpuscular hemoglobin concentration (MHCM) were calculated. Ten other ‘matrinxãs’ from the same groups were used to assess macrophage phagocytic activity and lipid levels. The results showed that females fed a probiotics-supplemented diet exhibited an increase in numbers of oocytes and, consequently, had higher rates of fertilization and hatching of larvae. Probiotic-treated fish also exhibited a significant increase in the phagocytic activity of macrophages, indicating an improvement in the immune system of breeders. Hematologic parameters were different in comparison to the time-zero group, and plasma cortisol and glucose levels were higher in the females. The total lipids levels in muscle and liver tissue were lower in B. amazonicus that received feed supplemented with probiotics.