Background Colorectal cancer is the fourth leading cause of cancer mortality. This study aims to compare the clinical outcomes of multidetector computed tomography (MDCT) with magnetic resonance imaging (MRI) for assessing mesorectal fascia (MRF) in patients with rectal cancer. Methods This research was a cross-sectional study of 60 patients with rectal cancer referred to two centers in Isfahan, Al-Zahra, and Seyed-al-Shohada hospitals. Considered parameters included sex, tumoral location, nodal involvement, as well as tumoral description. To assess the invasion of MRF in rectal cancer, researchers used MRI, axial MDCT, and multiplanar reconstruction CT scan (MPRCT). Sensitivity, specificity, and techniques’ positive and negative predictive values were measured. Also, to assess the statistical associations, the Kappa coefficient was used. Results There was no significant association between axial MDCT and MRI reports regarding MRF involvement (P>0.05). However, a statistical association was determined between the reports of multiplanar reconstruction CT (MPRCT) and MRI (P< 0.01, kappa=0.44). In addition, the association between MPRCT and MRI reports was statistically significant in patients with wall thickening and negative nodal involvement (Kappa = 0.699, P = 0.001). On the other hand, there was more agreement between MPRCT and MRI reports in patients with tumors in the middle or upper rectum. Conclusion The association between MRI and MPRCT reports regarding MRF involvement was statistically significant in patients with wall thickening and negative nodal involvement in the upper and middle rectum. Consequently, it is possible to replace MRI with the MPRCT method for assessing MRF in some patients.