Background and Objectives: Diarrhea induced by chemotherapy may represent a life-threatening adverse effect in cancer patients receiving chemotherapy. FOLFOX, an effective treatment for colon cancer, has been associated with diarrhea with high severity, particularly with higher doses. Management of diarrhea is crucial to increase the survival of cancer patients and to improve the quality of life. Glutamine is an abundant protein peptide found in blood and has a crucial role in boosting immunity, increasing protein anabolism, and decreasing the inflammatory effects of chemotherapy on the mucosal membranes, including diarrhea. This study aimed to provide evidence that parenteral L-alanyl L-glutamine dipeptide may have a positive influence on the incidence of diarrhea, treatment response, and the overall survival in colon cancer patients treated with modified FOLFOX-6 (mFOLFOX-6). Materials and Methods: Forty-four stage II and III colon cancer patients were included in this study where they were treated with the standard colon cancer chemotherapy mFOLFOX-6 and were randomly allocated into glutamine group and placebo group, each of 22 patients. Results: L-alanyl L-glutamine dipeptide was found to be significantly effective in decreasing the frequency and severity of diarrhea when compared to the placebo group, particularly after four and six cycles of mFOLFOX-6. There was no significant difference between the studied groups regarding to the overall survival. Conclusion: L-alanyl L-glutamine dipeptide can be considered as an add-on with chemotherapy to improve the quality of life and the overall survival of colon cancer patients.