Multiple beneficial properties of Opuntia ficus indica (OPF) are well established. In the present study, we have investigated the immunological role of OPF extract (OPFE) on murine splenocytes. OPFE dose- and time-dependently enhanced the proliferation of splenocytes without cytotoxicity. Our results also showed that the number of $CD4^+$ helper T cells and CD45R/$B220^+$ pan B cells increased markedly, but not $CD8^+$ cytotoxic T cells or $CD11b^+$ granulocytes/macrophages. In addition, OPFE significantly decreased the production levels of T helper (Th) 1 type cytokines, interferon (IFN)-$gamma$, and tumor necrosis factor (TNF)-$alpha$, although had no significantly differences in those of interleukin (IL)-4, a Th2 type cytokine in concanavalin A (Con A)-stimulated blastogenic cells. Furthermore, OPFE alone strongly increased IL-4 production and decreased TNF-$alpha$ production even in the absence of Con A. On the basis of these results, this study suggests that OPFE enhances immunity by regulating the pro- and anti-inflammatory response, indicating that this extract exerts a marked immunomodulatory effect, confirming its usefulness as therapy for immune-related diseases.