There is a large literature investigating the underlying mechanisms, risk factors and demographics of suicidal thoughts and behaviors across a number of psychiatric disorders, such as, major depression, anxiety and schizophrenia. However, less research has focused on the relationship between Post-Traumatic Stress Disorder (PTSD) and suicide. There were two broad aims of this review. The first was to assess the extent to which PTSD is associated with suicide, and the second was to determine the effects of co-morbid disorders on this relationship. Overall, there was a clear relationship between PTSD and suicidal thoughts and behaviors irrespective of the type of trauma experienced. Very few studies directly examined whether depression was a mediating factor in the relationships reported. However, where this was investigated, the presence of co-morbid depression appeared to boost the effect of PTSD on suicidality. It was noteworthy that hardly any studies had investigated concepts thought to be key in other domains of research into suicidality, such as, feelings of entrapment, defeat and hopelessness.