In the present study, Al2O3 coatings were deposited by plasma spraying using feedstock of different particle sizes. The effects of particle size on their velocity and temperature in the plasma jet, the microstructure and properties of the coatings were investigated. The results revealed that in view of the smaller inertia effects and lower heat capacity, the smaller particles can be easily accelerated and heated, and have higher in-flight velocity and temperature, which contributed to produce a denser coating with lower porosity and higher mechanical properties. It was also found that the coating deposited using the finest starting powder has the lowest thermal diffusivity. This may be reasonably correlated with the microstructural characteristics. In addition, the coating manufactured using the intermediate feedstock in terms of particle size (D50 of 19.3µm) exhibited the highest wear resistance.