Social threat avoidance is a crucial adaptive behaviour, but how these responses are learned and controlled remains unclear. Using a novel behavioural paradigm in mice, we demonstrate that social avoidance is stimulus-specific, not a generalized response. This avoidance depends on olfactory tubercle (OT) activity during the second threat exposure. Further, we identified a key brain circuit involved: the basolateral amygdala (BLA) to OT pathway. This pathway shows increased activity and synaptic plasticity specifically during threat assessment following a repeated social threat exposure. Crucially, avoidance behaviour is tightly regulated by neuromodulators. Serotonin (5-HT) release in the OT during the threat recall is essential for avoidance. Conversely, inhibiting serotonin shifts the balance, leading to dopamine (DA) release in the OT and promoting approach behaviour instead. These findings reveal that social threat avoidance is not a simple, generalized response. The OT plays a pivotal role in encoding how threatening a stimulus is, while the BLA-OT circuit integrates prior social experiences and modulates extinction. The delicate interplay between serotonin and dopamine finely tunes approach/avoidance decisions. This work offers crucial insights into the neural mechanisms underlying social learning, with potential implications for understanding social anxiety disorders.