Phosphorescent iridium(iii) complexes have gained increasing attention in biological applications owing to their excellent photophysical properties and efficient transportation into live cells. Their advantageous properties make them useful tools for enabling the intracellular detection of many different species for biological and medical applications. In this review, we summarize recent studies on the combination of iridium(iii) complexes and nanomaterials for intracellular sensing, drug delivery and photodynamic therapy. Various mechanisms and application modes are described and compared, and the outlook and future directions of this field are discussed as well.