Objective: To compare the diagnostic accuracies of ultrasound and magnetic resonance imaging (MRI) for deep (≥50%) myometrial invasion (DMI) and cervical stromal invasion (CSI) in women with endometrial cancer. Methods: This was a prospective study at a gynecology clinic for women with postmenopausal bleeding. Between October 2015–October 2018, consecutive women with suspected endometrial cancer based on ultrasound subjective pattern recognition were simultaneously assessed for DMI and CSI on ultrasound. Subsequently, they also underwent preoperative MRI. We compared the diagnostic accuracies of ultrasound and MRI in predicting DMI and CSI with the final histology as the gold standard. Results: We included 51 women. The prevalence of DMI and CSI were 22/51 (43%) and 7/51 (14%), respectively. The majority of malignancies were of endometrioid histological subtype (38/51, 75%) and FIGO stage 1 or 2 (40/51, 78%). Ultrasound diagnosed more cases of DMI compared to MRI (19/22 vs. 17/22), however, the difference was not statistically significant. The sensitivities and specificities of ultrasound and MRI for DMI were 86% vs. 77% and 66% vs. 76%, respectively. For CSI, ultrasound and MRI correctly diagnosed the same number of cases (5/7, 71%); their respective false-positive rates were low, 0/44 (0%) and 1/44 (2%). Ultrasound and MRI had a moderate agreement for DMI (κ=0.49; 95% confidence interval [CI]=0.26–0.73), whereas the agreement for CSI was substantial (κ=0.69; 95% CI=0.36–1.00). Conclusion Endometrial cancer can be simultaneously diagnosed and staged at women’s initial ultrasound assessment. The accuracies of ultrasound for DMI and CSI are comparable to MRI.