Abstract: The isotope effects of ablation processes in fusion plasma for five combinations of solid isotopic hydrogenic pellets H2, HD, D2, DT, and T2 have been studied for the first time to our knowledge. The results show that the modifications caused by isotope effects for pellet erosion speeds range from 1 for hydrogen pellet down to 0.487 for tritium pellet and are not negligible in ablation rate calculations. These effects can lead to deeper mass deposition and improved core fueling efficiency.