The aim of this study was to evaluate the influence of vitamin C supplementation in the diet of three-spotted piau fish (L. reinhardit), in terms of performance and production yield, analysis of nutritional chemical composition (carcass and fillet), as well as glycemic parameters. The experiment lasted 90 days. A total of 1040 fry were used, housed in 16 500 L rearing tanks. The design used was a randomized block design with four treatments and four replications. The control diet was designed to meet the vitamin C requirement according to commercial recommendations and the other diets were designed to contain extra dietary vitamin C supplementation levels (250, 500 and 750 mg ascorbic acid/kg diet). All the diets were isoproteic and isocaloric (28% CP and 3100 kcal/kg of feed). There was no significant effect of the regression on production performance and glycemic parameters. Thus, it was found that the inclusion of vitamin C at the commercial level was sufficient to provide productive performance, benefits for nutritional chemical composition and reduced handling and harvesting stress.