A series of Novel Mannich bases has been synthesized and evaluated $in$ $vitro$ cytotoxic activity against the human hepatocellular carcinoma (HepG2), human lung carcinoma (SK-LU-1), and human breast cancer (MCF-7). Compound $mathbf{9f}$ was found to be most potent against three cell lines with $IC_{50}$ values of 1.57, 1.16 and 1.21 ${mu}g$/mL, respectively. In addition, compounds $mathbf{9g}$, $mathbf{10f}$ exhibited very significant activity against MCF-7 cell line with $IC_{50}$ values of 2.0 ${mu}g$/mL.