"Fat talk" refers to conversations focused on body disparagement. We examined developmental changes in fat talk to avoid social rejection and the mediating role of fat talk between "thin-ideal" internalization and body dissatisfaction. A total of 214 high school girls and 227 college-aged women completed questionnaires assessing fat talk engagement, body dissatisfaction, thin-ideal internalization, and sensitivity to rejection. Path analyses showed that fat talk mediated between thin-ideal internalization and body dissatisfaction and that rejection sensitivity predicted fat talk among high school girls, but not among college women. The purpose of fat talk differed by developmental stage, suggesting that interventions for improving body image should be developmentally tailored.