This study explores the effects of dietary brown macroalgae (Ascophyllum nodosum) in- clusion on digestibility and blood biochemical indices and redox markers in piglets fed diets with varying levels (0%, 0.6% and 1%) of macroalgae from 18 to 64 days of age. Macroalgae significantly influenced lipid profiles, reducing total cholesterol levels (quadratic contrast p = 0.001) and demon- strating an increase in high-density lipoprotein cholesterol levels, particularly with 1% macroalgae inclusion (linear contrast p < 0.001), with a decrease in low-density lipoprotein cholesterol in both macroalgae-supplemented groups (linear contrast p = 0.001). Additionally, macroalgae had a positive impact on the activities of antioxidative enzymes (ferric-reducing ability of plasma, superoxide dismutase, reduced glutathione) and reduced lipid peroxidation products (lipid hydroperoxide, mal- ondialdehyde) in the blood, liver tissue, and intestinal epithelium of the ileum, suggesting enhanced antioxidative defense mechanisms. These changes were dose-dependent; in blood plasma, they exhibited both a linear and quadratic response, while in the tissues, the response was primarily linear. Additionally, an increase in the digestibility of crude fat in macroalgae-supplemented groups was observed (linear contrast p < 0.001), highlighting their potential role in improving nutrient absorption and digestion. The study findings emphasize the health benefits of natural, seaweed-based additives in diets, particularly in managing oxidative stress and improving lipid profiles, and highlight the potential of macroalgae as a natural dietary supplement to improve antioxidant systems and lipid metabolism in piglets.