Posttraumatic stress disorder (PTSD) and traumatic brain injury (TBI) are associated with increased risk for suicidal thoughts and behaviors. This chapter explores possible underlying neurocognitive and neuroanatomical factors related to PTSD and TBI that may contribute to increased susceptibility to suicidal thoughts and behaviors. The neurocognitive working model of suicidal behavior is used as a guiding framework (Jollant et al. 2011). Possible mechanisms involving altered modulation of value attribution, impaired regulation of emotional and cognitive responses, and facilitation of acts in an emotional context are explored within PTSD, TBI, and their co-occurrence. Discussion of clinical implications and limitations of this conceptual model, as well as directions for future research are provided.