Precise photothermal cancer therapy still relies on the development of multifunctional theranostic agents to integrate tumor-specific targeting, imaging, and therapy. In this study, we identified the zwitterionic near-infrared (NIR) fluorophore ZW800-Cl, an analog of the well-known ZW800-1, and found that it preferentially accumulated in tumors in various xenograft models. We have demonstrated that the optical and physicochemical properties of ZW800-Cl are similar to those of ZW800-1, but it has a unique tumor targetability. Since ZW800-Cl showed binding selectivity to cancer cells in vitro, it could be specifically targeted to xenograft models of multiple tumor types, including MCF-7, NCI-H460, and HT-29. The in vivo results of photothermal cancer therapy indicated that the xenograft tumors could be effectively ablated by the combination of ZW800-Cl and an 808 nm laser irradiation. In this regard, our finding may provide a new approach for developing multifunctional cancer theranostic agents, setting them apart from conventional nanoparticles based on inorganic and polymeric materials. Therefore, ZW800-Cl may hold promise as a multifunctional theranostic agent for tumor-targeted imaging and effective photothermal cancer therapy.