Catalysis-based chemodynamic therapy (CDT) is an emerging cancer treatment strategy which uses a Fenton-like reaction to kill tumor cells by catalyzing endogenous hydrogen peroxide (H₂O₂ T into a toxic hydroxyl radical (·OH). The performance of CDT is greatly dependent on PDT agent. Herein, mitochondria-targeting Pt nanoclusters were synthesized using cytochrome c aptamer (CytcApt) as template. The obtained CytcApt-PtNCs can produce ·OH by H₂O₂ under the acidic conditions. Moreover, CytcApt-PtNCs could kill 4T1 tumor cells in a pH-dependent manner, but had no side effect on normal 293T cells. Therefore, CytcApt-PtNCs possess excellent therapeutic effect and good biosafety, indicating their great potential for CDT.