Abstract Introduction Recently, clinical trials have commenced for cardiac regenerative therapy utilizing stem cells in patients with heart failure. Among the various transplantation approaches, there is a growing demand for less invasive methods to transplant sheet/patch-shaped cell products onto the heart surface, rather than resorting to conventional open surgery. This is particularly important considering the need for immunosuppressants due to allogeneic cell transplantation. Objective This study aims to develop a device for endoscopic transplantation of cell sheets onto the beating heart surface. Methods Prototype devices, initially developed in our prior study using a static heart model (Regenerative Therapy, 2020), were refined to better suit the cell sheet transplantation procedure onto a beating heart. We constructed a three-dimensional (3D) model of a beating heart located inside a thoracic cavity model, based on human computed tomography data and a 3D printer dedicated to simulating endoscopic surgical procedures. Human mesenchymal stromal cell (MSC)-derived cell sheets were prepared using temperature-responsive culture dishes and transferred onto a beating heart model pulsating at 80 beats per minute. We assessed the technical feasibility (N=8). Furthermore, skeletal muscle tissue was harvested from the thigh of the Clawn miniature pigs, and skeletal myoblasts were cultured from enzymatically digested tissue to create a cell sheet for autologous transplantation (8.0×10⁶ cells/sheet). Subsequently, the cell sheets labeled with Hoechst 33342 were endoscopically transplanted onto the pig heart surface (N=2). The pigs were sacrificed one week later, and the engraftment of the cell sheet was histologically evaluated. Results Successful deployment of MSC sheets onto the beating heart model was achieved in all procedures with one trial (100% success rate). The procedure duration from device insertion to the completion of cell sheet transplantation averaged 142±19 seconds. In experiments on autologous transplantation of myoblast cell sheets, two cases were successfully accomplished, with the transplanted cell sheet positive for Hoechst 33342 observed on the heart surface. Conclusion We have developed an endoscopic cell sheet delivery device using a pulsating heart model and a pig model, which holds promise for minimally invasive cardiac regenerative therapy in the future. Further investigations into the safety of the procedure are warranted for the clinical application of this system.