Obesity is now recognised as a major global health problem. It accounts for a large proportion of the population and is increasing in both developed and developing countries. Epidemiological evidence and studies in animal models showed that obesity increased the incidence of colon cancer. As obesity is difficult to prevent and treat, it is important to find effective approaches to prevent obesity-associated colon cancer. The prevention strategy should be different from that used for the treatment as clinically used drugs are not suitable for the prevention due to side-effects and cost. Phytochemicals are ideal for the prevention. This review summarises the effect of green tea component (-)-epigallocatechin-3 gallate and turmeric component curcumin in the prevention of obesity-associated colon cancer and the mechanisms for their preventive effects. Both agents have been demonstrated to reduce obesity increased polyp formation in animal models and inhibit PI3K/Akt and MAPK signal pathways.