The　biomedical　features　of　metal　clusters　have　been　explored　in　tumor　diagnostic　applications　in　recent　years.　Peptide　or　protein　protected　metal　clusters　with　low　toxicity,　ultra-small　size　and　good　biocompatibility　are　ideal　bioanalytical　tools,　and　exhibit　better　cancer　diagnostic　properties　that　have　been　attractive　to　oncologists.　This　perspective　provides　a　rigorous　but　succinct　overview　of　cancer　diagnosis　as　a　working　concept　for　metal　clusters　by　reporting　the　latest　significant　advances　in　the　applications　of　metal　clusters　in　tumor-related　bioanalysis　and　diagnosis.　The　materials　design　principles,　bioanalytical　mechanisms　and　biomedical　applications　of　metal　clusters　are　described,　and　then　the　potential　challenges　and　prospects　of　metal　clusters　in　cancer　diagnosis　are　discussed.　A　perspective　addressing　the　role　of　metal　clusters　in　this　field　is　required　to　understand　their　effects　and　functions,　as　well　as　for　the　scientific　community　to　further　advance　the　development　of　metal　clusters　for　broader　diagnostic　applications.