In this study, we describe the development of a novel tissue marker that can be injected from within the digestive tract by using an endoscopic instrument, and visualized using near-infrared (NIR) fluorescence imaging. The marker was prepared in three steps, (i) mixing NIR-fluorescent indocyanine green (ICG) with giant vesicles (GVs) of lecithin, (ii) suspending the ICG-containing giant vesicles (ICG-GV) in an oil phase dissolving polyglycerol-polyricinoleate (PGPR), and (iii) centrifugation of the suspension layered on a buffered solution to obtain a giant polymer vesicle (polymerasome) containing ICG-GV. We injected the tissue marker into the inner gastric surface of an anesthetized pig using an endoscopic syringe, and observed the injection site using a fluorescence laparoscopic camera. The diameter of the spot blur was approximately 2 cm over a 5-h period, demonstrating the utility of this procedure as a tissue marker for tumor marking, and suggesting its potential for assisting navigation during surgical procedures.