Eleven diarylurea derivatives (1a–1k) bearing N-methylpiperazinyl moiety were synthesized by the reaction of isocyanate with arylamine. The structures of 1a–1k were characterized by 1 H-NMR and MS. The cytotoxic activities of 1a–1k were evaluated via MTT method against human lung adenocarcinoma epithelial cell line A549 and human prostate carcinoma cell line PC3. Compounds 1d and 1k displayed potent cytotoxic activity. The results suggested that the activities are considerably related to the substituent group at another phenyl ring.