BackgroundPrisoners are a vulnerable population with higher rates of trauma than community populations. Social support is important for both in–prison adjustment and post-release community re-entry. Loneliness, a related construct to social support, has been found to be associated with elevated rates of suicidal ideation and behavior, depression, and hopelessness in incarcerated populations.MethodsThis study explored the relationship of past physical, sexual, and crime-related trauma to current perceived social support and loneliness in a mixed-gender sample of 235 depressed prisoners enrolled in depression treatment studies.ResultsHistory of any trauma, regardless of type, as well as physical, sexual, and crime-related traumas were associated with lower current perceived social support scores (controlling for gender). Past sexual trauma and crime-related trauma were associated with higher levels of loneliness (controlling for gender), though history of any trauma and physical trauma was not.ConclusionFindings suggest that both overall trauma and specific types of trauma are linked to perceived social support and loneliness among incarcerated persons with major depressive disorder. This is the first study, to the authors’ knowledge, that specifically observed a relationship between past trauma and current social support and loneliness in prison populations. Many intervention programs for prisoners encourage them to develop non-criminogenic and substance-free social networks. These programs should be aware that individuals who have experienced interpersonal trauma may have additional interpersonal challenges, and may need strategies to address interpersonal deficits related to trauma exposure.Electronic supplementary materialThe online version of this article (doi:10.1186/2194-7899-2-7) contains supplementary material, which is available to authorized users.