Oil-resin of Copaifera multijuga Hayne is popularly used due to its anti-inflammatory properties. In this study, we evaluate the effects of the bark ethanolic extract on Ehrlich tumor cells. For extract preparation, bark was removed from stem and chopped into smaller pieces. Most were dried and grounded. The first extract was made with hexane, followed by ethyl acetate. Absolute ethanol was added to the residue and extract was filtered and concentrated (EtOH). In vitro cytotoxic activity of the EtOH was analyzed on both spleen and tumor cells. For evaluation of in vivo activity, Ehrlich carcinoma bearing Swiss mice were daily treated with different concentration of EtOH during 30 days. Evaluation of in vitro cell viability showed that 1mg/ml extract is cytotoxic to spleen and tumor cells. Evaluation of in vivo tumor development showed that treatment with 200mg/kg of EtOH was able to reduce in 45.28% the tumor growth. Treatment for 7 days increased IL-12p70, IFN-γ and TNF-α production and for 14 days reduced the lymphoproliferative activity in both tumor bearing and mice healthy. Our results show that the ethanolic extract of copaiba bark affect Ehrlich tumor cells, reducing their cell viability in vitro as well as their development in vivo.