Aim: A Pt(II)-terpyridine compound, bearing two piperidine substituents at positions 2 and 2′ of the terpyridine ligand (1), is highly cytotoxic and shows a mechanism of action distinct from cisplatin. 1 has been incorporated within the ferritin nanocage (AFt). Materials & methods: Spectroscopic and crystallographic data of the Pt(II)–AFt nanocomposite have been collected and in vitro anticancer activity has been explored using cancer cells. Results: Pt(II)-containing fragments bind His49, His114 and His132. Pt(II)–AFt nanocomposite is less cytotoxic than 1, but it is more toxic than cisplatin at high concentrations. The Pt(II)–AFt nanocomposite triggers necrosis in cancer cells, as free 1 does. Conclusion: Pt(II)–AFt nanocomposites are promising vehicles to deliver Pt-based drugs to cancer cells.