Cancer cells represent a heterogeneous population characterized by unregulated proliferation. Research indicates that certain enzymes display markedly increased expression levels in neoplastic tissues compared to normal tissues. Clinically referred to as tumor biomarkers, these enzymes are pivotal to cancer cell growth, invasion, and metastasis. Fluorescent dye-based techniques enabling visualization of such overexpressed enzymes facilitate early tumor diagnosis and provide guidance for fluorescence-assisted tumor resection. Activity-based aggregation-induced emission luminogens (AIEgens) have garnered significant attention from researchers due to their distinct advantages over traditional fluorescent dyes, such as the reversed aggregation-caused quenching (ACQ) phenomenon, enhanced imaging fidelity, and superior sensitivity. In this entry, we comprehensively review the design strategies of enzyme-activatable AIEgens targeting tumor-overexpressed enzymes and discuss their biomedical applications in cancer cell and tumor imaging. The entry concludes with an overview of the current challenges and outlook in this area.