A series of cationic cyclometalated iridium(III) complexes with o-carborane cage on the main ligand of 2-phenylbenzothiazole were synthesized. The prepared iridium complexes (C1-C6) were fully characterized by UV-vis, NMR, and FT-IR spectra. The exact molecular structure of complex C1 was further studied by single crystal X-ray diffraction analysis. The different substitution position of o-carborane on the 2-phenylbenzothiazole ring lead to obvious differences in the emission properties of the synthesized complexes. The o-carboranyl unit results in a bathochromic shift of 10 nm in the fluorescence emission spectrum of C2. In addition, the presence of an o-carborane fragment promoted the strong fluorescence intensity of C1 and C4, which can be used as a tool to effectively boost the intensity of fluorescence properties. The emission fluorescent behavior of iridium(III) complexes can be facilely tuned by structural variations in the main ligands of these materials.