<p>A 63-day experiment was conducted to assess the impact of using eight levels of <i>Monascus purpureus</i> pigment (0, 25, 50, 75, 100, 150, 200, and 300 mg kg⁻¹) along with a commercial pigment, astaxanthin (Lucantin^® Pink; 150 mg kg⁻¹), in the diet on the growth performance, fillet quality, and hemolymph biochemical indices of juvenile crayfish (4.71±0.23 g) at three replicates. An increment in the supplemented levels of <i>Monascus</i> pigment (50–300 mg kg⁻¹) in the diet of crayfish showed significant increases in most growth and feed efficiency indices when compared with the control and astaxanthin diet (<i>p</i>&lt;0.05). The highest final weight (24.35 g), protein efficiency ratio (PER) (3.13), and protein productive value (PPV) (58.38%) were observed in the crayfish fed the diet containing 200 mg kg⁻¹ <i>Monascus</i> pigment (<i>p</i>&lt;0.05). The highest levels of phenoloxidase, superoxide dismutase, lysozyme, and nitric oxide synthase were measured in the hemolymph of crayfish fed the diet containing 200 mg kg⁻¹ <i>Monascus</i> pigment (<i>p</i>&lt;0.05). The evaluation of fillet color quality showed that crayfish fed the diet containing 300 mg kg⁻¹ of <i>Monascus</i> pigment had the highest values for the a* and b* indices (<i>p</i>&lt;0.05). The optimum dietary levels of <i>Monascus</i> pigment on final weight, specific growth rate, and feed conversion ratio of crayfish, based on the broken-line regression model, were 225.6, 227.1, and 228.4 mg kg⁻¹, respectively. The results of the present study showed that the use of <i>Monascus</i> pigment at levels of 225 to 230 mg kg⁻¹ can have a positive effect on growth performance, fillet color quality, and immune responses of tested crayfish. Further studies are recommended to investigate the use of <i>Monascus</i> pigment in the diets of other aquatic species, particularly crustaceans, to determine optimal inclusion levels and evaluate potential benefits.</p>