Reaction of 1,3,4-oxadiazolyl-phenylthiourea 3 with hydrazonoyl halides gave the corresponding 1,3,4-oxadiazolylimino-1,3,4-thiadiazoles. Also, treatment of 3 with ethyl chloroacetate and -haloketones afforded the corresponding thiazolidinone and thiazole derivatives, respectively. The structures of the synthesized products were confirmed by spectral data. Ten compounds were evaluated for their anti-cancer activity against the colon carcinoma cell line (HCT-116). The results revealed that 1,3,4-thiadiazole derivatives 13d and 19c (IC50=0.73 and 0.86 mu g/mL, respectively) have promising antitumor activity against colon carcinoma (HCT-116), and most of the tested compounds showed moderate anti-cancer activity.