New azo dyes bearing 2-pyridone and benzimidazole moieties were prepared using diazotization of 4-(1H-benzo[d]imidazol-2-yl)aniline and coupling of the obtained diazonium salt with substituted 3-cyano-2-pyridones. Obtained compounds were characterized via UV-Vis, FT-IR, and H-1 and C-13 NMR spectroscopy as well as by elemental analysis data. The UV-Vis spectra of the synthesized dyes were measured in thirteen solvents of different properties at room temperature. Solvatochromism and tautomerism of novel azo dyes were discussed. An MTT (3,4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide) test was performed to prove the biocompatibility of the investigated dyes. The investigated dyes exhibited satisfying antiproliferative activities against both tumor cell lines, MDA-MB-231 and HCT-116, demonstrating the potent capacity for treatment of tumors.