The aim of this study was to assess the diagnostic performance of computed tomography (CT) for initial staging of non-endometrioid carcinomas of the uterine corpus. Waiving informed consent, the Institutional Review Board approved this Health Insurance Portability and Accountability Act (HIPAA)-compliant retrospective study of 193 women with uterine papillary serous carcinomas, clear cell carcinomas, and carcinosarcomas, who underwent surgical staging between May 1998 and December 2011 and had preoperative CT within 6 weeks before surgery. Two radiologists (R1, R2) independently reviewed all CT images. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and area under the curve were calculated using operative notes and surgical pathology as the reference standard. The respective sensitivities and specificities achieved by R1/R2 were 0.79/0.64 and 0.87/0.75 for detecting deep myometrial invasion (MI) on CT; 0.56/0.63 and 0.93/0.79 for detecting cervical stromal invasion; 0.52/0.45 and 0.95/0.93 for detecting pelvic nodal metastases; and 0.45/0.30 and 0.98/0.98 for detecting para-aortic nodal metastases. Although CT had suboptimal sensitivity for the detection of omental disease, it had high PPV for omental seeding at surgical exploration (1.00 for R1 and 0.92 for R2). Inter-observer agreement ranged from moderate in the detection of deep MI (κ = 0.42 ± 0.06) to almost perfect in the detection of para-aortic nodal metastases (κ = 0.88 ± 0.08). In patients with uterine non-endometrioid carcinomas, CT is only moderately accurate for initial staging but may provide clinically valuable information by ‘ruling-in’ isolated para-aortic lymph node metastases and omental dissemination.