•Stressful experiences can be transmitted among individuals through social interactions.•Rodent studies of vicarious social defeat stress and social defeat stress crossover are reviewed.•The vicarious experience of social defeat is associated with a host of physiological and behavioral deficits.•Social interaction with a stressed partner in the aftermath of social defeat elicits stress responses.•These models can be useful for studying the neurobiological processes underlying the contagion of stress across individuals. Stressful experiences can be transmitted among individuals through social interactions. Like humans, rodents are social creatures whose behavior and physiology can be influenced by the emotional state of fellow rodents. This paper will review rodent studies which have explored two conditions of potential social stress contagion using the social defeat paradigm. In the vicarious social defeat model, mice and rats that witness a conspecific being socially defeated exhibit physiological stress responses and develop a host of depressive- and anxiety-like behavioral deficits. Likewise, social interaction with a stressed partner in the aftermath of social defeat stress results in physiological stress responses and social avoidance behavior. After summarizing the existing literature on this newly emerging area of social defeat stress contagion in rodents, we will discuss the potential utility of these rodent models for investigating the neurobiological processes and sensory channels of information that allow for the spread of psychophysiological effects of stress across individuals.