Intracellular pathogens are mainly eliminated by cell-mediated immunity offered by phagocytic cells like neutrophils, macrophages and monocytes. Two tannin glycosides, 1-O-galloyl-6-O-luteoyl-α-D-glucopyranoside (1) and 3-O-methylellagic acid 3'-O-α-rhamnopyranoside (2) were isolated from the ethyl acetate fraction (EF) of the methanol leaf extract of Phyllanthus muellerianus. The structures of the isolated compounds were elucidated by 1H-NMR and by mass spectroscopy. The effects of the isolated compounds on phagocytic competence of macrophages and neutrophils using in vitro models were evaluated. Compounds 1 and 2 significantly (p<0.05) increased both phagocytic ability and intracellular killing capacity of neutrophils. This study established that the tannin glycosides stimulated cell-mediated innate immunity by increasing the phagocytic function of neutrophils and thus may be useful in both the clinical and prophylactic treatment of intracellular microbial infections.