We investigated the efficacy of a Rumex crispus and Cordyceps sinensis mixture made using the Beopje (Korea traditional processing method to remove anti-nutrients and enhance phytochemicals) method to regulate immune cell responses toward nitric oxide (NO) production, pro-inflammatory cytokines, and inflammation related genes in mice splenocytes. The six experimental groups were as follows: control (control), Rc-Cs (Rumex crispus (Rc) and Cordyceps sinensis (Cs) mixture, 6:4), TMC (Taemyeongcheong, commercial healthy drink containing Rc-Cs), LPS (lipopolysaccharide), LPS+Rc-Cs, and LPS+TMC. The Rc-Cs mixture reduced nitric oxide (NO) production in LPS-induced splenocytes. Moreover, Rc-Cs enhanced production of the pro-inflammatory cytokines TNF-α, IFN-γ, IL-1β, and IL-6 compared to the control (no treatment). However, Rc-Cs inhibited production of pro-inflammatory cytokines in LPS-induced splenocytes. In addition, LPS+Rc-Cs also significantly suppressed mRNA expression of IL-1β and IL-6 compared to LPS treatment. Interestingly, Rc-Cs did not increase mRNA levels of iNOS and COX-2, which are inflammation related genes compared to the control, while LPS+Rc-Cs reduced mRNA levels of iNOS and COX-2 compared LPS alone (p < 0.05). TMC showed a similar pattern compared to Rc-Cs. Therefore, Rc-Cs treatment in splenocytes enhanced NO production and pro-inflammatory cytokines compared to the control, whereas Rc-Cs treatment in LPS-induced splenocytes reduced NO production, pro-inflammatory cytokines, and inflammation related genes. Thus, Rc-Cs regulated immune cells responses by increasing pro-inflammatory cytokines in splenocytes and reducing toxin (LPS)-induced inflammation. These results indicate that a Rumex crispus and Cordyceps sinensis mixture (Rc-Cs) and TMC containing Rc-Cs promote immune cells responses and anti-inflammatory activities.