A series of novel ruthenium(II)–cymene complexes (1–8) containing substituted pyridyl–thiazole ligands, [Ru(η6‐p‐cymene)(L)Cl]Cl (L = N,N‐chelating derivatives), have been synthesized and characterized using elemental analysis, infrared, 1H NMR and 13C NMR spectroscopies and mass spectrometry. All these complexes not only display marked cytotoxicity in vitro against three different human cancer cell lines (HeLa, A549 and MDA‐MB‐231), but also exhibit promising anti‐metastatic activity at sub‐cytotoxic concentrations. Cell cycle analysis shows that the ruthenium(II) complex‐induced growth inhibition was mainly caused by S‐phase cell cycle arrest. Further protein level analysis suggests that compound 5 may exert antitumor activity via a p53‐independent mechanism.