Cancer is the second leading cause of death after cardiovascular disease. The causative factors of cancer are related to a variety of factors including genetic environmental psychosocial and dietary factors of which the impact of dietary factors on cancer has been a major concern. Whole grains retain endosperm germ and bran and are a good source of dietary fiber B vitamins minerals and other nutrients. Epidemiological studies have shown that regular consumption of foods based on whole grains and their products can reduce the risk of cancer such as colorectal cancer breast cancer and esophageal cancer. Much of this health advantage is related to the presence of dietary fibre polyphenols bioactive peptides and other natural functional components in whole grains. The active ingredients in whole grains achieve cancer prevention and treatment by promoting gastrointestinal motility and protecting intestinal health reducing inflammation levels and enhancing immunity reducing obesity risk and improving insulin resistance as well as inducing cancer cell cycle arrest and promoting cancer cell apoptosis among other ways. This paper summarizes the epidemiological evidence of whole grains for cancer prevention as well as the preventive and therapeutic effects of dietary fiber active peptides and phenolics on cancer and describes the underlying mechanisms aiming to provide a scientific basis for improving the dietary intake of whole grains.