Group IV metal complexes have previously shown promise as novel anticancer agents. Here, we discuss the mechanistic and cytotoxic nature of a series of group IV β‐diketonate coordination complexes. Clear evidence that the ligands are exchangeable on the metal centre and that the β‐diketonate ligands can act as potential drug delivery vehicles of the group IV metal ions was obtained. When evaluated for the cytotoxicity against human colon adenocarcinoma (HT‐29) and human breast adenocarcinoma (MCF‐7) cell lines, a general trend of decreasing potency down the group IV metals was observed. The most promising results obtained were for the hafnium complexes, with the tris diphenyl β‐diketonate hafnium complex exhibiting IC50 values of 4.9±0.9 μM and 3.2±0.3 μM against HT‐29 and MCF‐7, respectively, which are comparable with the activity of cisplatin against the same cell lines. This tri β‐diketonate hafnium complex is the first to show potent in vitro cytotoxic activity. The results reported show that ligand design has a significant effect on the cytotoxic potential of the complexes, and that these group IV complexes warrant further evaluation as novel metal‐containing anticancer agents.