Alchornea cordifolia is commonly used by African populations for its healing properties. However, the cell toxicity of this plant for optimal safe use is still a concern. The objective of this study was to assess the cytotoxicity activity of aqueous and methanolic leaf extracts of Alchornea cordifolia. The cytotoxicity activity of Alchornea cordifolia leaf extracts was investigated on healthy human umbilical endothelial cells (HUVEC), human malignant liver cancer cells (HEP-G2) and on human malignant lung cancer cells, alveolar epithelium (A549). The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium-bromide (MTT) colorimetric method was used to evaluate the ability of living cells to reduce the yellow-coloured MTT to its metabolite, the blue-coloured formazan. The number of living cells after 72 hours of incubation was proportional to the intensity of purple staining measured by flow cytometry. On the living cells, the methanolic and aqueous extracts were not toxic. The viability rates were 53.56 ± 2.17% and 55.60 ± 0.30%, respectively and with doxorubicin it was 19 ± 1% (p = 0.0021). On malignant cells, the methanolic and aqueous extracts did not show any toxicity either. The viability rates of HEP-G2 malignant cells were 71.35 ± 0.23% and 81.44 ± 3.95%, respectively, while that obtained with doxorubicin was 39 ± 1% (p = 0.05). The viability rates of A549 malignant cells were 51.07 ± 1.97% and 44.84 ± 6.22%, respectively whereas that of doxorubicin was 25 ± 3% (p = 0.05). The methanolic and aqueous leaf extracts of A. cordifolia were not toxic for healthy cells. The safe use of this plant in traditional medicine has now been demonstrated. Also, this plant has not been shown to be toxic to cancer cells, and therefore should not be used in the treatment of cancer.