Anxiety disorders are the most prominent mental disorder in the United States, and women are 60% more likely than men to have an anxiety disorder. One hypothesis for this sex difference is faster fear generalization rates in females. In previous studies using male subjects, context change disrupted a fear response at a short, but not long retention interval. An incidental observation suggested that females would show a different temporal pattern of fear generalization. In Experiment 1, male and intact female rats displayed disrupted fear responses in a novel context at 1 day. Males displayed context discrimination at all intervals, whereas females exhibited generalization by 5 days. In Experiment 2, ovariectomized females were given an empty capsule or a capsule containing 17β-estradiol to determine the role of estrogens in fear generalization. Female rats with no hormone replacement displayed context discrimination at 5 days, whereas those receiving estradiol generalized their fear response to a novel context. These results demonstrate that fear generalization for contextual cues occurs faster in female rats and that this effect is mediated, in part, by estrogens. Understanding the sex differences in fear generalization is likely to be critical to developing effective treatments for anxiety disorders.