Obesity is a growing epidemic all over the world that by virtue of inducation of a chronic, low-grade, and systemic inflammation leads to an increased risk of a number of diseases, including cancer. IL-6 an important cytokine in the increased risk to cancer in obese patients mainly because of its pro-inflammatory activity. Some data suggest that IL-6 might increase the risk of certain cancers such as those that originate from breast, liver, prostate, colon, and esophagus. A better understanding of the regulation and role of IL-6 in obesity-associated cancer is required to develop effective therapeutic approaches.