In-flight spheroidization of alumina powders in Ar-H-2 (H-2-7.6%, vol/vol) and Ar-N-2 (N-2-13.0%,, vol/vol) RF induction plasmas was investigated numerically and experimentally. The mathematical model for the plasma flows incorporates the k-epsilon turbulence model, and that for particles is the Particle-Source-in-Cell (PSI-Cell) model. Experimental results demonstrate that spheroidized alumina particles are produced in both Ar-H-2 and Ar-N-2 RF plasmas, with different particle size distributions and crystal phases. Agreement between the predicted and measured particle size distributions is satisfactory under high particle feed rate conditions, while the results obtained for the Ar-H-2 plasma are better than those for the Ar-N-2 plasma. The discrepancy occurring in low feed rate conditions suggests that particle evaporation is an important factor affecting the plasma-particle heat transfer.