Re-education of tumor-associated macrophages (TAMs) toward antitumor effectors may be a promising therapeutic strategy for the successful treatment of cancer. HangAmDan-B (HAD-B), a herbal formula, has been used for stimulating immune function and activation of vital energy to cancer patients in traditional Korean Medicine. Previous studies have reported the anti-angiogenic and anti-metastatic effects of HAD-B; however, evidence on the immunomodulatory action of HAD-B was not demonstrated. In the present study, immunocompetent mice were used to demonstrate the suppression of the in vivo growth of allograft Lewis lung carcinoma (LLC) cells, by HAD-B. In addition, HAD-B inhibited the in vitro growth of LLC cells by driving macrophages toward M1 polarization, but not through direct inhibition of tumor cell growth. Furthermore, culture media transfer of HAD-B-treated macrophages induced apoptosis of LLC cells. Results of the present study suggest that the antitumor effect of HAD-B may be explained by stimulating the antitumor function of macrophages. Considering the importance of re-educating TAMs in the regulation of the tumor microenvironment, the present study may confer another option for anti-cancer therapeutic strategy, using herbal medicines such as HAD-B.