This paper presents a comprehensive theoretical study on electron mobility in highly doped polycrystalline SnO2 thin films, a widely employed material in modern devices. Our physical model incorporates phonon-electron interaction, ionised impurity, and grain boundaries as scattering mechanisms, effectively explaining the temperature and electron density-dependent variation of electron mobility in doped polycrystalline SnO2 thin films. We highlight the significant influence of trap density at grain boundaries, the self-compensation effect, and average grain size on the theoretical limit of electron mobility. At a doping level of 1019 cm−3, the limit is estimated at 100 cm2.V−1.s−1, while for 1020 cm−3, it reduces to 50 cm2.V−1.s−1. These factors are strongly influenced by deposition conditions, including temperature, precursor chemistry, and deposition atmosphere. By analysing Hall mobility with respect to carrier density, temperature, or film thickness using our model, a better understanding of the limiting mechanisms in electron mobility can be achieved. This knowledge can guide the development of appropriate experimental strategies to enhance electron mobility in highly doped polycrystalline SnO2 films for advancing the performance of SnO2-based devices across various applications.