Macleaya cordata (M. cordata) is a herbal plant that has abundant amounts of sanguinarine, which has many biomedical properties. The effects of M. cordata dietary supplementation on the productive performance, some blood constituents, and growthrelated genes’ expression were evaluated in turkey. M. cordata extract was dietary supplemented to turkey at levels of 25, 50, and 100 ppm and a control group. Growth performance measurements (FBW, ADG, and FCR) and production efficiency factor for turkey (BPEF) were similar (p > 0.05) in all supplemented groups. M. cordata has no adverse effects (p > 0.05) on the birds’ health regarding hematological (Hb, RBCs, WBCs, and PCV) and blood biochemical indices evaluating liver function, kidney function, and lipid profile. Moreover, the mRNA expression of growth-related genes, such as growth hormone receptor (GHR), insulin-like growth factor 1 (IGF-1), cyclooxygenase 3 (COX-3), adenine nucleotide translocase (ANT), and uncoupling protein 3 (UCP-3) were upregulated (p < 0.001) in M. cordata treatments with the highest value for SG50 compared with the control group. We concluded that exogenous M. cordata dietary supplementation upregulated the expression of growth-related genes in turkey at a level of 50 ppm without adverse effects on their health status regarding hematological and biochemical indices.