Background New methods to reduce subjectivity in preoperative magnetic resonance imaging (MRI) staging of endometrial cancer are needed. Purpose To investigate the role of MRI quantitative assessment in staging and risk stratification of endometrial cancer. Material and Methods Preoperative T2-weighted (T2W) images and diffusion-weighted imaging of 42 patients were analyzed retrospectively by two radiologists. Tumor area ratio (TAR) and tumor volume ratio (TVRseg) were calculated by semi-automatic segmentation of the tumor and uterus on T2W imaging and apparent diffusion coefficient (ADC). TVR was also calculated by the 3D metric method (TVRmetric). Mean ADC(tumor) was calculated. The patients were allocated to risk groups regarding the stage, grade, and lymphovascular invasion (LVI) status. Results TAR, TVRmetric, T2W TVRseg, and ADC TVRseg showed a significant difference between the superficial and deep myometrial invasion groups (P < 0.001). All of these parameters showed a good diagnostic performance for detecting deep myometrial invasion (AUC>0.82), the highest accuracy rate (85%) was found with T2W TVRseg. LVI was significantly associated with TAR (P = 0.002) and T2W TVRseg (P = 0.014), while the cervical invasion was associated with TAR (P = 0.03). ADC(tumor) was significantly lower in high-grade tumors (P = 0.002). There was a significant difference in ADC(tumor) (P = 0.002), TAR (P = 0.004), and T2W TVRseg (P = 0.038) between the low- and high-risk groups. AUC of TAR and T2W TVRseg for detecting high-risk groups were 0.80 and 0.77, respectively, while AUC of ADC(tumor) for the low-risk group was 0.75. Conclusion MRI quantitative assessments such as TAR, TVR, and ADC(tumor) may improve the accuracy of preoperative staging and can help in risk stratification of endometrial cancer.