Breast cancer is the second most common type of cancer after lung cancer and the fifth most common cause of cancer death. Several structural classes of compounds were discovered against tumor, but many of the existing antitumor agents exhibit severe side effects. Hence there is a need to identify a novel chemical entity having a broad range of therapeutic activity with fewer side effects. In this direction, several imidazolyl-(4-oxoquinazolin-3(4H)-yl)-acetamides 1-4(a-d) were screened for their antitumor activity against Ehrlich Ascites Carcinoma (EAC) using in-vitro and in-vivo models. Compounds 4b, 4d, and 3a showed highly significant antitumor activity against EAC in comparison with vincristine as standard.