Real-time and continuous monitoring of systemically administered agents is an important task in pharmaceutical development. Herein, we performed a real-time continuous study of the pharmacokinetics and biodistribution of indocyanine green (ICG) and liposomal indocyanine green (Lipo-ICG) in vivo by multispectral optoacoustic tomography (MSOT). By comparing the blood clearance and uptake behavior of these two ICG formulations in liver, spleen, kidney and tumor, we showed that Lipo-ICG prolonged the retention time of ICG in blood, and resulted in enhanced accumulation and retention in liver, spleen, and tumor. The results obtained from the MSOT test provided a comprehensive and continuous view of the metabolic behavior of the injected agents in different formulations. The results may also be helpful for understanding this new imaging technique.