<p>Fluorescence-based optical imaging and sensing technologies have been used for preclinical and clinical disease diagnosis. In contrast to traditional fluorophores, aggregation-induced emission luminogens (AIEgens) present several advantages, including enhanced fluorescence signals in the aggregated state, large Stokes shift, excellent photostability and controllable excited-state energy dissipations for fluorescence imaging, as well as simultaneous phototherapy. A variety of AIEgens have been designed to address conditions such as cancer, infections and cardiovascular diseases. In this Review, we discuss the biomedical applications of AIEgens in bioimaging and phototheranostics from a clinical and translational perspective, with emphasis placed on their property modulation principles and functionalization strategies. We also address the limitations and challenges that hinder their further development, and explore opportunities to accelerate their in vivo clinical translation.</p>