Two series of steroidal dienamides 4a-q and 5a-f were designed, synthesized and evaluated for cytotoxic activities against five human cancer cell lines (MGC-803, EC109, PC-3, SMMC-7721 and MCF-7). The protocol developed efficiently achieved the construction of carbon-carbon double bond and selective conversion of nitrile group into carboxamide in one-pot procedure. Besides, compounds 4a-q and 5a-f showed moderate to excellent cytotoxic activities with the IC₅₀ values ranging from 0.1 to 40 μM and most of them were more potent than 5-fluorouracil. Particularly, four compounds 4d, 4e, 4q and 5a showed excellent selectivity against MGC-803 with the IC₅₀ values less than 1 μM. Flow cytometry analysis demonstrated that compound 4c caused the cellular early apoptosis and cell cycle arrest in G2/M phase in a concentration-independent manner.