Abstract We present the analysis of the first lunar‐based observational characterization of the Earth’s plasmasphere and ionosphere using Global Navigation Satellite Systems signals tracked from the lunar surface by the Lunar GNSS Receiver Experiment (LuGRE). The Earth‐Moon geometry enables limb sounding of the plasmasphere at altitudes exceeding 3,000 km, bridging a critical observational gap. We compared Total Electron Content measurements from GPS and Galileo satellites’ signals with predictions from the Global Core Plasma Model. While the model captures the general morphology of the plasmasphere, significant discrepancies emerge in the ionosphere/plasmasphere transition region. Specifically, LuGRE data reveal a overestimation of electron density by the model during the dayside phase indicating a lower plasma refilling efficiency than currently parameterized and an underestimation during the nightside phase. These results demonstrate the capability of lunar‐based GNSS measurements to continuously monitor the global plasma environment, paving the way for future permanent observatories on the Moon.