Acute social defeat was induced by using a social aggressive attack according to the intruder–resident paradigm. The social behavior of the intruder mice toward novel contexts and objects was measured on days 1, 3, 7, and 15 after aggression. The expression of IEGs in the BLA, vHIP, and mPFC was analyzed at 2 h after behavioral test. The results indicated that social fear and avoidance were significant on days 1–3 after aggression and were accompanied by a high expression of IEGs in the BLA and a low expression of IEGs in the vHIP and mPFC. On days 7–15 after aggression, the social interaction gradually increased and was accompanied by a low expression of IEGs in the BLA and a high expression of IEGs in the vHIP. Inhibiting the function of BLA after aggression ameliorated social defeat, which suggested that BLA consolidates social fear. This study posited that social defeat can be treated by suppressing the consolidation or prompting the extinction of aversive stimulations.