Oyster mushroom slices (Pleurotus ostreatus) were exposed to ɣ-radiation as a pretreatment and solar dried to investigate the influence of irradiation on drying kinetics. Processing conditions included exposure of mushrooms to 0 kGy (control), 0.5 kGy, 1.0 kGy, 1.5 kGy and 2.0 kGy of ɣ-radiation at a dose rate of 1.7 kGy/h and drying at a mean temperature of 53.2±6.4°C. Experimental drying data were fitted to 5 thin layer drying models by non-linear regression. Irradiation was observed to enhance the drying rate of mushroom slices, with higher doses causing faster moisture removal. Drying characteristics of slices exposed to lower dosages were best described by Page’s model (R2 =0.9878, 0.9967, 0.9925 correspondingly for “control” (0.0 kGy), 0.5 and 1.0 kGy while the Diffusion model best fit the data for those exposed to higher doses of radiation (R2 =0.9938, 0.9890 for 1.5 and 2.0 kGy respectively). Deff ranged from 1.88 to 2.44 x 10-08 and increase from “control”, 0.5 kGy, 1.0 kGy, 1.5 kGy to 2.0 kGy. Irradiation of mushrooms as a pretreatment for drying increases moisture diffusivity and drying rate with higher doses having the most effect.