Updated project metadata. Tumor Progression Locus 2 (TPL-2) kinase mediates Toll-like Receptor (TLR) activation of ERK1/2 and p38 MAP kinases in myeloid cells to modulate expression of key cytokines in innate immunity. This study identified a novel MAP kinase-independent regulatory function for TPL-2 in phagosome maturation, an essential process for killing of phagocytosed microbes. TPL-2 catalytic activity was demonstrated to induce phagosome acidification and proteolysis in primary mouse and human macrophages following uptake of latex beads. Quantitative proteomics revealed that blocking TPL-2 catalytic activity significantly altered the protein composition of phagosomes, particularly reducing the abundance of V-ATPase proton pump subunits. Furthermore, TPL-2 stimulated the phosphorylation of DMXL1, a critical regulator of V-ATPases, to induce phagosome acidification. Consistent with these results, TPL-2 catalytic activity was required for phagosome maturation and the efficient killing of Staphylococcus aureus following phagocytic uptake by macrophages. These results indicate that TPL-2 controls the innate immune response of macrophages to bacteria via V-ATPase induction of phagosome maturation.