Taiwanofungus camphoratus is a unique medicinal mushroom endemic to Taiwan, and it is used as a folk medicine in East Asian countries. The aim of the present study was to investigate the immunomodulatory effects of “leader Antrodia cinnamomea capsule” (LAC), a health food product containing solid-state cultivated mycelial powder of T. camphoratus. For the in vivo studies, mice were orally administered LAC (76, 250, and 760 mg/kg b.w.) for 30 days, and its effects on cell-mediated humoral immune function were examined. The results of the concanavalin A-induced splenic lymphocyte proliferation test showed that LAC significantly increased splenic lymphocyte proliferation compared with the control. In addition, serum hemolysin analysis showed that LAC treatment significantly increased the half value of serum hemolysin (HC50) in mice compared with the control. Moreover, treatment with LAC significantly increased the phagocytic index as measured by carbon clearance and natural killer cell activity. Taken together, these findings provide strong evidence that LAC can modulate immune function.