The effect of drying air temperature on drying characteristics of oyster mushrooms were investigated in this study. Different sizes of mushrooms were used to evaluate the effects of size of the mushrooms on drying processes in natural convection solar dryer. Full and half mushrooms were dried in a natural convection solar dryer until the samples reached desired moisture content of 8.2%. Air temperature inside and outside the dryer, wind velocity, relative humidity and moisture loss were also measured at every two hours interval until the samples reached desired moisture content. The moisture loss from the samples was measured at every one-hour interval. The experimental results show that the size of the mushroom has considerable effects on the moisture removal. In this study, average moisture content, average drying rate and drying duration values of full mushrooms were found to be 3.79 %, 0.2 g min-1and 22 hours. Average moisture content, average drying rate and drying duration values of half mushrooms were found to be 5.2 %, 0.214g min-1 and 16 hours respectively. The results revealed that among different sizes of mushroom, half mushrooms produced better quality product than full mushrooms during the drying process in the natural convection solar dryer.