This study aimed to observe the immunomodulatory effects of oligopeptides derived from jackfruit (Artocarpus heterophyllus Lam.) (JOPs). 200 female BALB/c mice in five groups were respectively given deionized water (control), whey protein (0.20 g per kg body weight (BW)) and JOPs at doses of 0.20, 0.40, and 0.80 g per kg BW by intragastric administration on a daily basis. 7 tests were conducted to determine the immunomodulatory effects of JOPs on immune organ indexes, cellular and humoral immune responses, macrophage phagocytosis, and natural killer (NK) cell activity. Spleen T lymphocyte sub-populations and serum cytokine and immunoglobulin levels were tested to study how JOPs improved the immune system. We found that JOPs could significantly enhance innate and adaptive immune responses in mice by the improvement of cell-mediated and humoral immunity, macrophage phagocytosis capacity and NK cell activity. The immunomodulatory effects may be based on increased T and Th cell percentages, serum interleukin (IL)-1α, IL-10, tumor necrosis factor (TNF)-α, production of immunoglobulin (Ig) M, IgG, and IgA, and depressed interferon (IFN)-γ secretion. These results suggest that dietary JOPs could be valuable as potential immunomodulators.