Objective: Synthesis, characterization and evaluation of quinolin-2-one derivatives as possible anticancer agents. Methods:A series of novel 4-hydroxy-1-phenyl/methyl-3-(3-substituted-1-(substitutedimino)propyl)quinolin-2(1H)-one derivatives IIa(1-5)/IIb(1-5) and 4-hydroxy-1-phenyl/methyl-3-(1-(substituedimino)ethyl)quinolin-2(1H)-one derivatives IIIa(1-3)/IIIb(1-3) were synthesised by nucleophilic addition of substituted anilines on 3-acetyl-4-hydroxy-1-phenyl/methylquinolin-2(1H)-one (a/b) and 4-hydroxy-3-(3-substitutedpropanoyl)-1-phenyl/methyl quinolin-2(1H)-one (Ia/Ib); respectively. The synthesised derivatives were characterised by spectral analysis and were tested for their in vitro anticancer activity against K562 and Hep 3b cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay method.Results: The compounds were tested for their in vitro anticancer activity against K562 and Hep 3b cell lines at 10, 20, 25, 30 and 50 µg/ml concentration using MTT assay method. The compound 4-hydroxy-3-(3-morpholino-1-(phenylimino)propyl)-1-phenylquinolin-2(1H)-one (IIa-1) showed anticancer activity with IC50 value 20 µg as compared to the control against K562 cell lines. The compound 4-hydroxy-1-phenyl-3-(1-(phenylimino) ethyl) quinolin-2(1H)-one (IIIa-1) showed anticancer activity with IC50 value less than 10 µg. Conclusion:The proposed method for the synthesis of novel derivatives is convenient and gives a good yield. Some of the synthesised compounds showed promising anticancer activity against K562 and Hep 3b cell lines. Compound IIa-1 (R=-C6H5; R1= morpholine; R2= C6H5-NH-) exhibited most potent activity against K562 cell lines. Compound IIIa-1 (R=-C6H5; R3= C6H5-NH-) has been proved to be the most cytotoxic compound among the other derivatives against Hep 3b cell lines.