A cyclometalated ruthenium (II) complex 1 [(Ru (Phen)2(Pbznh)]+ PF6− (Phen = 1,10‐phenanthroline and Pbznh = N‐(4‐(pyridine‐2‐yl)benzylidene) nicotinohydrazide) with nicotinohydrazide as a functional group was synthesized and characterized. Changes of its absorption spectra and color induced by Cu2+ and Fe3+ were systematic investigated. The results demonstrated that complex 1 could be served as a colorimetric probe to fast, selective and sensitive detection of Cu2+ and Fe3+ both in acetonitrile and filter paper based strips. Upon addition of Cu2+ and Fe3+ to solution of probe 1, solution color changed from pink to colorless and light yellow respectively, and their corresponding detection limit were calculated to be 3.26 × 10−8 M and 3.12 × 10−7 M. Moreover, color of test papers with 1 changed from pink to colorless/yellow when Cu2+/Fe3+ were dropwise added. Therefore, it can be used as a desirable ‘naked‐eye’ indicator candidate for Cu2+ and Fe3+.