Abstract: Exosomes are important substances involved in intercellular signal transduction and have high biological values. Accordingly, exosomes have become a research hotspot. Highly specific and sensitive exosome-tracing method is the key to revealing the biological function of exosomes. Exosome tracing relies mostly on molecular imaging and its advantages focus primarily on nuclear-medicine molecular imaging, which includes direct and indirect radionuclide-labeling methods. Nuclear-medicine molecular imaging could be combined with anatomical imaging to quantitatively monitor exosome distribution and could be used to evaluate the therapeutic effect of exosomes. It plays an extremely important role in exosome tracing. This paper reviews the biological value of exosomes and the research progress in tracing exosomes through nuclear-medicine molecular imaging.