Colorectal cancer (CRC) is the most common gastrointestinal cancer, and a significant health care problem globally. Dietary factors, for example high meat consumption and deficiency of fiber, calcium, vitamin D, and folate, are well-recognized to be associated with a risk of developing CRC. Colonic microbiota, by living in a mutual relationship and participating in key metabolic functions that compliment host physiology, is crucially important in the maintenance of our health. A state of imbalance in host–microbe homeostasis, termed dysbiosis, is associated with several diseases, including CRC. Epidemiological studies have revealed strong associations between diet, microbiota, and CRC. Substantial in-vitro and in-vivo evidence suggests that the dynamic composition and diversity of colonic microbiota are affected by alteration of the diet, and that the balance between the beneficial and detrimental microbial metabolites is of crucial importance in mediation of the dietary risk factors of colonic carcinogenesis. A better understanding of complex diet–microbiota–CRC relationships can help us understand how diet affects the risk of CRC and will provide a more scientific approach to the development of novel strategies to prevent CRC.