Reduced social motivation is a hallmark of individuals with autism spectrum disorders (ASDs). Although the exact neural mechanisms are unclear, oxytocin has been shown to enhance motivation and attention to social stimuli, suggesting a potential to augment social reinforcement learning as the central mechanism of behavioral interventions in ASD. We tested how reinforcement learning in social contexts and associated reward prediction error (RPE) signals in the nucleus accumbens (NAcc) were modulated by intranasal oxytocin. Male adults with a childhood diagnosis of ASD (n = 15) and healthy controls (n = 24; aged 18-26 years) performed a probabilistic reinforcement learning task during functional magnetic resonance imaging in a single-center (research center in Germany), randomized double-blind, placebo-controlled cross-over trial. The interventions were intranasal oxytocin (Syntocinon®, Novartis; 10 puffs = 20 international units (IUs) per treatment) and placebo spray. Using computational modeling of behavioral data, trial-by-trial RPE signals were assessed and related to brain activation in NAcc during reinforcing feedback in social and non-social contexts. The order of oxytocin/placebo was randomized for 60 participants. Twenty-one participants were excluded from analyses, leaving 39 for the final analysis. Behaviorally, individuals with ASD showed enhanced learning under oxytocin when the learning target as well as feedback was social as compared to non-social (social vs. non-social target: 87.09% vs. 71.29%, 95% confidence interval (CI): 7.28-24.33, p = .003; social vs. non-social feedback: 81.00% vs. 71.29%, 95% CI: 2.81-16.61, p = .027). Correspondingly, oxytocin enhanced the correlation of the RPE signal with NAcc activation during social (vs. non-social) feedback in ASD (3.48 vs. -1.12, respectively, 95% CI: 2.98-6.22, p = .000), whereas in controls, this effect was found in the placebo condition (2.90 vs. -1.14, respectively, 95% CI: 1.07-7.01, p = .010). In ASD, a similar pattern emerged when the learning target was social (3.00 vs. -0.64, respectively, 95% CI: -0.13 to 7.41, p = .057), whereas controls showed a reduced correlation for social learning targets under oxytocin (-0.70 vs. 2.72, respectively, 95% CI: -5.86 to 0.98, p = .008). The current data suggest that intranasal oxytocin has the potential to enhance social reinforcement learning in ASD. Future studies are warranted that investigate whether oxytocin can potentiate social learning when combined with behavioral therapies, resulting in greater treatment benefits than traditional behavior-only approaches.