The histologic grade of endometrioid adenocarcinoma (EMCA) is one of the important factors in choosing a treatment plan. Currently, needle biopsy or surgical resection is necessary to diagnose the histological grade; a less invasive procedure is strongly desired. In this study, we evaluated the utility of amide proton transfer (APT) imaging in estimating the histologic grade of EMCA. APT signal intensities (SIs) of EMCA increased in accordance with the progression of histologic grade. APT SIs of high-grade EMCA were significantly higher than those of low-grade EMCA. APT imaging has potential as a biomarker for histologic grade of EMCA.