Three studies investigated implicit biases, and their modifiability, against overweight persons. In Study 1 (N = 144), the authors demonstrated strong implicit anti-fat attitudes and stereotypes using the Implicit Association Test, despite no explicit anti-fat bias. When participants were informed that obesity is caused predominantly by overeating and lack of exercise, higher implicit bias relative to controls was produced; informing participants that obesity is mainly due to genetic factors did not result in lower bias. In Studies 2A (N = 90) and 2B (N = 63), participants read stories of discrimination against obese persons to evoke empathy. This did not lead to lower bias compared with controls but did produce diminished implicit bias among overweight participants, suggesting an in-group bias.