Objective To explore the MRI findings of diffuse midline gliomas with H3K27M mutation, and help us understand this new entity and improve the accuracy of diagnosis. Methods The clinical and imaging data of 17 diffuse midline gliomas with H3K27M mutation confirmed by pathology were retrospectively collected from July 2016 to April 2018 in Guangdong Sanjiu Brain Hospital. All patients were performed with pre?contrast and post?contrast MRI examination. All images were analyzed according to the location, shape, boundary, solid or cystic, signal feature, enhancement feature, and degree of edema. Results (1) Location:Six cases located in thalamus,4 cases located in brainstem,1 located in hypothalamus, 6 cases had multiple lesions in the midline and/or involving one or more brain. (2) Morphology and boundary:Seven cases had regular shape and clear boundary, 10 cases had irregular shapes and unclear boundaries. (3) Necrosis, cystic degeneration, hemorrhage: Twelve cases had necrosis or cystic degeneration in varying degree, 4 cases had hemorrhage. (4) Signal and enhancement features: The solid component showed slightly?low or low signal on T1WI, and slightly?high or high signal on T2WI; the cystic component showed obvious low signal on T1WI and obvious high signal on T2WI. T1WI enhancement:Eight cases showed uneven light?moderate enhancements, and all cases were adults; Six cases showed significant enhancements with large or small rings; Three cases showed uneven obvious enhancement. (5) Peritumoral edema: Fourteen cases had mild peritumoral edema,1 case had moderate peritumoral edema,2 cases had obvious peritumoral edema. Conclusion The MRI findings of diffuse midline gliomas with H3K27M mutation had certain characteristics,which can help to improve the level of diagnosis and differential diagnosis.