The aim of the present study was to evaluate the effect of maize replacement by crude biodiesel-derived glycerol on the zootechnical performance, chemical carcass composition and blood parameters of silver catfish (Rhamdia quelen) juveniles. A total of 600 silver catfish juveniles were distributed in a completely randomized design with six treatments comprised of isoproteic and isoenergetic pelleted diets with six levels of glycerol replacing maize, and five replicates. The glycerol maize substitution significantly influenced (p < 0.05) the final weight, clean trunk production and headless carcass yield, with the highest values for both parameters observed in the 100% substitution treatment, significantly different compared to the 0% replacement treatment. Plasmatic calcium, alkaline phosphatase, glucose, total proteins, oxaloacetic and pyruvic glutamic transaminase concentrations were not influenced (p < 0.05) by the dietary treatments, nor were moisture, crude protein and mineral matter (p < 0.05). Crude glycerol can be included in up to 7.5% in juvenile silver catfish diets. Biodiesel-derived glycerol can, thus, successfully replace maize in juvenile silver catfish diets.