Carbonic anhydrase IX (CAIX) is a transmembrane protein that is specifically overexpressed on the surface of hypoxic tumor cells. With the function of regulating the acidity of tumor cells both inside and outside, CAIX is closely related to tumor proliferation, invasion and metastasis. Therefore, CAIX is a promising target for tumor imaging and therapy. Herein, we summarized recent advances in CAIX-based tumor imaging, therapy and theranostics, and prospected future applications of using CAIX as an anti-tumor target.