Aims:To evaluate the effect of the microwave disinfection on the dimensional changes of the heatcured acrylic resin. Materials and Methods: Heat-cured acrylic resin was used in this study. Thirty two disk-shaped specimens with reference points were prepared to evaluate the linear dimensional changes of the heat-cured acrylic resin that sterilized by microwave irradiation and by chemical solutions chlorhexidine and sodium hypochlorite. The specimens were divided into four tested groups, eight specimens for each group. Group I as control group and other groups divided according to the sterilization method. The dimensional change was evaluated with an Electronic Digital Caliper. Mean values wear compared statistically with: One-way Analysis of Variance (ANOVA), followed by Duncan ' s Multiple Range Test to determine the significant different among the tested groups at (p≤0.05) level of significance. Results: They showed that there was a highly significant difference of the means values of the linear dimensional change among the four tested groups. Specimens sterilized by microwave irradiation have a higher value than that sterilized by the chemical solutions. Conclusions:The results of this study appeared that sterilization by the microwave irradiation produce a significant effect on the dimensional stability of the heat-cured acrylic resin, while sterilization by chemical solution produce no significant difference.