Synchronous endometrial and cervical cancer is a very rare condition. This report describes a case of a 46-year-old woman who presented with a cervical mass that measured 5.6 cm along its longest diameter, whose biopsy analysis revealed an endocervical mucinous adenocarcinoma. She was classified as having an IB2 cervical carcinoma and treated with concurrent chemoradiation plus hysterectomy. Pathological and immunohistochemical analysis of the surgical specimens revealed a synchronous endometrioid grade 2 adenocarcinoma in the endometrium, and a well-differentiated mucinous adenocarcinoma in the cervix. Magnetic resonance imaging (MRI) studies performed prior to treatment were reviewed and apparent diffusion coefficient (ADC) maps were generated. The ADC values demonstrated distinct signal intensity differences between the endometrial and endocervical tumors. In conclusion, diffusion-weighted MRI and ADC maps can help to distinguish the site of origin of synchronous tumors.