Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has garnered considerable attention in recent years, owing to its precise spatiotemporal accuracy with minimal side effects. Recent research reveals that the combination of PDT and PTT exhibits a remarkable anti‐tumor efficacy compared to PDT or PTT alone, which has put forward the new requirements of multifunctional phototherapy agents with both high photosensitization and photothermal conversion efficiencies. Among the newly developed multifunctional agents, the ones with one or two 3‐dicycanovinylindan‐1‐one (IC) moieties as the acceptors attract much more attention, due to their long‐wavelength excitation and emission, as well as high phototherapy efficacies. Therefore, in this review, the latest advancement of multifunctional agents based on IC acceptor is summarized. Especially, we focus on the structure–property relationships of the agents, as well as their biomedical application in anti‐tumor therapy or image‐guided therapy. Our perspective on the further future development of this field is also discussed to conclude. 3‐Dicycanovinylindan‐1‐one has been recently widely used to construct multifunctional phototheranostic agent for fluorescence image‐guided simultaneous photodynamic therapy (PDT) and photothermal therapy (PTT), due to its advantage in balancing electron‐withdrawing ability and spin‐orbit coupling. Herein, the design principle, structure–property relationship, biomedical application, as well as several challenges and opportunities of this type of phototheranostic agent are discussed in detail in this review.