Real-time intraoperative guidance is essential during oncological surgery for complete and safe tumour resection. Fluorescence imaging in the near-infrared spectrum has shown potential for guiding surgeons during complex interventions. Recently, there has been a shift towards the use of fluorescence contrast agents for molecular imaging. The first targeted fluorescent agents, of which most consist of approved therapeutic antibodies conjugated to a fluorescent dye, have been evaluated in several early-phase clinical trials. Moreover, advances in protein engineering and drug design have led to the development of a variety of tracers suitable for molecular fluorescence image-guided surgery. In this Review, we discuss preclinical and clinical evidence, ongoing clinical trials, and the latest developments in the field of molecular near-infrared tracers for fluorescence-guided cancer surgery.