Highly fluorescent iridium nanoclusters were synthesized and investigated its application as a potential intracellular marker. The iridium nanoclusters were prepared with an average size of ∼2 nm. Further, these nanoclusters were refluxed with aromatic ligands, such as 2,2′-binaphthol (BINOL) in order to obtain fluorescence properties. The photophysical properties of these bluish-green emitting iridium nanoclusters were well characterized by using UV-Visible, fluorescence and lifetime decay measurements. The emission spectrum for these nanoclusters exhibit three characteristic peaks at 449, 480 and 515 nm. The fluorescence quantum yield of BINOL-Ir NCs were estimated to be 0.36 and the molar extinction co-efficients were in the order of 106 M -1cm-1. In vitro cytotoxicity studies in HeLa cells reveal that iridium nanoclusters exhibited good biocompatibility with an IC 50 value of ∼100 μg/ml and also showed excellent co-localization and distribution throughout the cytoplasm region without entering into the nucleus. This research has opened a new window in developing the iridium nanoparticle based intracellular fluorescent markers and has wide scope to act as biomedical nanocarrier to carry many biological molecules and anticancer drugs. © 2013 Springer Science+Business Media New York.