In rectal carcinomas, the rate of pelvic recurrence is quite high with surgery and adjuvant chemoradiotherapy (CRT). Therefore, neoadjuvant chemoradiotherapy (CRT) is used increasingly in rectal cancers. In our study, we aimed to reveal the CRT response in rectal cancers and to determine which clinical-morphological prognostic parameters are effective in predicting the treatment response. Forty-six patients with rectal cancer diagnosed between 2016-2019 and treated with neoadjuvant CRT were included in the study. The cases were re-examined by two pathologists for prognostic parameters and tumor regression grade (TRG). Modified Ryan Scoring system was used to evaluate TRG. Data showing Microsatellite instability (MSI) status with some parameters such as tumor diameter and distant metastasis before treatment were obtained by searching patient files on the computer. Nineteen of the 46 cases were female and 27 were male. Forty-four of the cases are classical adenocarcinoma and 2 of them are mucinous adenocarcinoma. According to TRG, which was used to evaluate the treatment response, 1 (2.2%) of the cases showed complete response (Score 0); 8 (17.4%) showed near-complete response (Score 1); 18 (39.1%) showed partial response (Score 2) and 19 (41.3%) showed no response or poor response (Score 3). A statistically significant relationship was found among prognostic parameters only between tumor grade and treatment response (p = 0.021). Response to treatment after CRT is in the inverse ratio to the pathological grade of the tumor. The treatment response is better in low grade tumors. In patients with rectal cancer and treated with neoadjuvant CRT, survival is determined not by the pre-treatment clinical staging, but rather by the pathological staging, which includes TRG after treatment. Tumor response to CRT is also effective in planning adjuvant chemotherapy in patients with rectal cancer.