Abstract: Tetrastigma hemsleyanum is a plant resource with promising medicinal potential. To evaluate the effects of its stem and leaf extract (THNE) as a phytogenic feed additive on the health of Litopenaeus vannamei, we cultured shrimp haemocytes in vitro and treats them with different concentrations of T. hemsleyanum stem and leaf extract to determine the cell viability, phagocytic activity, phenoloxidase activity, and respiratory burst intensity. We established five treatment groups (A0−A4) with graded extract supplementation levels (0, 1, 2, 4 and 8 g·kg⁻¹) and conducted a 56-day feeding trial, then analyzed the variations in shrimp growth performance, serum biochemical parameters, immune indices, and antioxidant indicators were analysed. The results show that within the concentration range of 25−2 000 μg·mL⁻¹, the stem and leaf extract of THNE caused no significant change in cell viability (p>0.05), and could significantly activate the immune response of hemocytes (p<0.05). Aquaculture experiments revealed that dietary supplementation with 1−4 g·kg⁻¹ of the extract significantly increased the weight gain rate of shrimp and improved serum lipid metabolism, manifested as elevated levels of beneficial lipoproteins and reduced triglyceride and transaminase contents (p<0.05). Meanwhile, the extract significantly enhanced hemocyte phagocytic activity, phenoloxidase activity, and respiratory burst, while effectively increasing the activities of alkaline phosphatase, acid phosphatase, lysozyme, glutathione peroxidase, superoxide dismutase, and catalase in serum (p<0.05). These results indicate that supplementing the diet with 2 g·kg⁻¹ of THNE extract can significantly improve the growth performance, immunity, and antioxidant capacity of L. vannamei.