When experiencing negative emotions, individuals often reach out for social support to help regulate their emotions. In times of an acute crisis, however, close friends might not be available, and physical closeness might be impossible. This functional magnetic resonance imaging (fMRI) study investigated the effect of social proximity on the effectiveness of social support for regulating emotions and the underlying neural mechanisms. Participants regulated their emotions in response to negative images either alone (intrapersonal regulation), or with help of a picture and supporting sentence provided by the best friend, or by a stranger (interpersonal regulation). Regulation success was enhanced for the support of friends compared to regulating alone or with the support of strangers. This effect was accompanied by the interplay of large-scale brain networks involved in processing emotions, social cognition, and cognitive control. Interpersonal regulation appeared to be implemented by lateral prefrontal regions. The amygdala showed increased activation for strangers. The activation profile of the social cognition network suggests a role in supporting empathic and mentalizing processes. The results highlight the power of social connectedness for boosting emotion regulation ability and the different neural networks that contribute to this effect.