Sodium caseinate (CasNa) induces differentiation and M-CSF production in mouse band granulocytes in vitro; however, it is not yet known if this molecule can also induce the proliferation and activation of the granulocyte lineage in vivo. In this work we evaluated the induction in vivo of granulopoiesis and the activation of granulocytes in mice treated with CasNa. BALB/c male mice 8-12 weeks old were used. The animals were inoculated intraperitoneally with 1 ml of CasNa (10% in PBS p/v) four times (every 48 h). Granulocyte proliferation was evaluated by flow cytometry; activation was evaluated by phagocytic indices. The cytokine was measured using an ELISA assay. We show that CasNa increased bone marrow granulopoiesis percentage (38.35 ± 10.88 vs. 64.94 ± 34.14 BrdU+/Gr-1+ cells) and the granulocytes generated presented increased phagocytic indices (0.3 ± 0.1 vs. 0.6 ± 0.11, p