Through the analysis of case studies of chimpanzees (Pan troglodytes troglodytes) in residence at a sanctuary, who previously sustained prolonged captivity and biomedical experimentation, we illustrate how human psychological models of diagnosis and treatment might be approached in great apes. This study reflects growing attention to ethical, scientific, and practical problems associated with psychological well-being of animals. The analysis concludes that a diagnosis of Complex PTSD in chimpanzees is consistent with descriptions of trauma-induced symptoms as described by the DSM-IV and human trauma research. We discuss how these findings relate to diagnosis and treatment of chimpanzees in captivity and the issue of their continued laboratory use. This clinical study contributes toward theory and therapeutic practices of an emergent trans-species psychology inclusive of both humans and other species. Such an ability to extend what we know about models of human trauma opens deeper understanding and insights into ourselves as well as individuals from other species.