A new series of novel benzimidazole derivatives containing barbitone moiety (5a–f) was synthesized by a Knoevenagel condensation of (2E)-1-(1H-benzimidazol-2-yl)-3-phenylprop-2-en-1-ones (4a–f) and barbituric acid in the presence of catalytic amount of acetic acid medium. All the final structures were assigned on the basis of IR, 1 H NMR and mass spectra analysis. Acute toxicity studies were performed initially to determine the safety of titled derivatives and the ED50 value was calculated 50 mg/kg. All the final derivatives were screened for antitumour activity against Dalton's ascitic lymphoma in mice. All the new candidates at a dose of 50 mg/kg showed a good antitumour activity against DLA-bearing mice when compared to the standard 5-fluro uracil. Among the final derivatives (5e), 5-[(2E)-1-(1H-benzimidazol-2-yl)-3-(3-nitrophenyl) prop-2-en-1-ylidene] pyrimidine-2,4,6(1H,3H,5H)-trione was found to be most potent antitumour in nature.