This study aimed to synthesize quinolinone derivatives and investigate their cytotoxic activity. The compound 1-azacoumarin-3-carboxylic acid (2-oxo-1H-quinoline-3-carboxylic acid) was obtained via the cyclocondensation of 2-hydroxybenzaldehyde with diethyl malonate in base catalyst to give ethyl coumarin-3-carboxylate, followed by the ammonolysis of ester (ethyl coumarin-3-carboxylate) with ammonia in the presence of anhydrous potassium carbonate. Treatment of 2-oxo-1H-quinoline-3-carboxylic acid with acetic anhydride, cinnamaldehyde, cinnamic acid and methyl 5-phenyl-2-cyano-2,4-pentadienoate under different conditions led to the formation of 1 (substituted) aza coumarin-3-carboxylic acids (1-N-(acetyl)-azacoumarin-3-carboxylic acid, 1-N-(2-Formyl-1-phenyl) vinyl-azacoumarin-3-carboxylic acids, 1-N-[2-(Hydroxy) carbonyl-1-(Phenyl) vinyl]-azacoumarin-3-carboxylic acid and 1-N-(4-Cyano-5-methoxy-5-oxo-1-Phenylpenta-1,3-diene-1-y)-azacoumarin-3-carboxylic 284 acid), respectively. The structures of synthesized 1-(substituted) azacoumarin-3-carboxylic acids were confirmed based on spectroscopic methods (IR and NMR), along with elemental analyses. Interestingly compound 6 demonstrated probable impacts as an anti-cancer drug against the MCF-7 cell line. The mechanism of action was assessed using a flow cytometric assay. The outcomes revealed that compound 6 could arrest the cell cycle at G2/M phase and pre-G1 apoptosis.