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Sheath blight (ShB) caused by <i>Rhizoctonia solani</i> is a major disease of rice, seriously affecting yield; however, the molecular defense mechanism against ShB remains unclear. A previous transcriptome analysis of rice identified that <i>R. solani</i> inoculation significantly induced <i>MDPK</i>. Genetic studies using <i>MDPK RNAi</i> and overexpressing plants identified that <i>MDPK</i> positively regulates ShB resistance. This MDPK protein was found localized in the endoplasmic reticulum (ER) and Golgi apparatus. Yeast one-hybrid assay, electrophoresis mobility shift assay (EMSA), and chromatin immunoprecipitation (ChIP) showed that the intermediate domain proteins IDD12, IDD13, and IDD14 bind to the <i>MDPK</i> promoter. Moreover, IDD14 was found to interact with IDD12 and IDD13 to form a transcription complex to activate <i>MDPK</i> expression. The three IDDs demonstrated an additive effect on <i>MDPK</i> activation. Further genetic studies showed that the <i>IDD13</i> and <i>IDD14</i> single mutants were more susceptible to ShB but not <i>IDD12</i>, while <i>IDD12</i>, <i>IDD13</i>, and <i>IDD14</i> overexpressing plants were less susceptible than the wild-type plants. The <i>IDD12</i>, <i>IDD13</i>, and <i>IDD14</i> mutants also proved the additive effect of the three <i>IDDs</i> on <i>MDPK</i> expression, which regulates ShB resistance in rice. Notably, <i>MDPK</i> overexpression maintained normal yield levels in rice. Thus, our study proves that IDD12, IDD13, and IDD14 activate <i>MDPK</i> to enhance ShB resistance in rice. These results improve our knowledge of rice defense mechanisms and provide a valuable marker for resistance breeding.