The ethanolic crude extract from the leaves of banaba (Lagerstroemia speciosa L.) was investigated for its potential hemocyte count effect in vivo. Three doses of the extract ranging from the maximum non dose, one-half and one-fourth of that dose were administered via intraperitoneal route on female Swiss mice. Initialhemocyte count was determined before treatment and on3, 6, and 10 post-treatment days. The maximum non-lethal dose and one-half of that dose were effective in increasing all hemocyte counts over time. One-th of that dose was effective in increasing the WBC and platelet count but its effect on the RBC count was on a decreasing manner on the earlier days of treatment. We concluded that the banaba leaf ethanolic extract produced an increasing effect on WBC and platelet count but not RBC count. Results indicate that the banaba leaf ethanolic extract has a potential for use in increasing the platelet count of a dengue patient.