The immediate social context at the time of drug consumption is critical at modulating it. The neurobiological substrate of such an influence is however poorly documented. The presence of a stranger peer, naïve to the drug, has been shown to reduce recreational cocaine intake in rats with similar results in human cocaine users. Here we assessed its influence in rats having previously lost their control over drug consumption. The subthalamic nucleus (STN) has been shown to play a critical role in cocaine motivation, escalation and re-escalation, as well as compulsive drug seeking. We show here that after escalation of cocaine intake, the presence of a stranger peer drastically reduced cocaine intake. The same effect was observed after both optogenetic inhibition and high-frequency stimulation of the STN in absence of a peer. We further show that the beneficial influence of social presence is mediated via the STN. One Sentence Summary The presence of a stranger peer drastically decreases cocaine intake after drug escalation, as does a subthalamic optogenetic modulation.