Implicit theories of body weight (ITBW) have predicted successful weight loss efforts, such that incremental beliefs (body weight is malleable) lead to more success and resilience in the face of setbacks than entity beliefs (body weight is unchangeable). But, less is known about how ITBW is related to body image. Two studies tested how ITBW (measured in Study 1, manipulated in Study 2) interacts with body mass index (BMI) to predict body shame, body surveillance, and disordered eating in undergraduate samples (Study 1 N = 296, Study 2 N = 363). We saw evidence that for participants with higher BMIs, an incremental theory of body weight predicted less body shame, surveillance, and disordered eating compared to an entity theory of body weight. But, for participants with lower BMIs, we saw some evidence that an incremental theory of body weight can actually be harmful and increase disordered eating attitudes or a desire to change body weight.