Background Social deficits and dysregulations in dopaminergic midbrain-striato-frontal circuits represent transdiagnostic symptoms across psychiatric disorders. Animal models suggest that modulating interactions between the dopamine and renin-angiotensin system with the angiotensin receptor antagonist Losartan (LT) can modulate learning and reward-related processes. We have therefore determined the behavioral and neural effects of LT on social reward and punishment processing in humans. Methods A pre-registered randomized double-blind placebo-controlled between-subject pharmacological design was combined with a social incentive delay fMRI paradigm during which subjects could avoid social punishment or gain social reward. Healthy volunteers received a single-dose of LT (50mg, n=43) or placebo (n=44). Reaction times and emotional ratings served as behavioral outcomes, on the neural level activation, connectivity and social feedback prediction errors were modelled. Results Relative to placebo, LT switched reaction times and arousal away from prioritizing punishment towards social reward. On the neural level the LT-enhanced motivational salience of social rewards was accompanied by stronger ventral striatum-prefrontal connectivity during reward anticipation and attenuated activity in the ventral tegmental area (VTA) and associated connectivity with the bilateral insula in response to punishment during the outcome phase. Computational modelling further revealed an LT-enhanced social reward prediction error signal in VTA and dorsal striatum. Conclusions LT shifted motivational and emotional salience away from social punishment towards social reward via modulating distinct core nodes of the midbrain-striato-frontal circuits. The findings document a modulatory role of the renin-angiotensin system in these circuits and associated social processes, suggesting a promising treatment target to alleviate social dysregulations.