Homelessness is a complex problem which has significant implications on an individual and societal level. There is strong evidence to suggest that amongst the contributory factors to becoming homeless, mental health problems and an increased vulnerability to substance misuse and addiction feature highly. Furthermore, traumatic events are often seen as contributory factors to mental health difficulties and substance misuse, whilst trauma experience has been identified as a risk factor for homelessness. Prevalence rates for psychological disorders related to trauma in high risk groups, such as war veterans, are significantly higher than the general population and as many as 6 per cent of homeless people are ex-Armed Forces personnel. The first section of this thesis is a narrative literature review summarising the existing literature linking trauma and homelessness and examining the current research for an association between trauma experienced during military service and homelessness. In addition, the clinical implications linked to the present diagnostic process and treatment approaches for trauma-related disorders are considered. The second section of this thesis is a qualitative study undertaken to explore the experiences of ten individuals, seven males and three females, residing in a homeless hostel who gave their accounts during semi-structured interviews. Interpretative Phenomenological Analysis was utilised in an effort to gain insight into the meaning of trauma within the lived experience of homelessness. The themes produced relate to the construal of the homelessness pathway, the impact of homelessness, and coping; with additional overarching themes of trauma and responsibility. The findings illustrate that the factors that influence the onset and maintenance of homelessness are complex and multifaceted and reflect the uniqueness of individual participant’s accounts whilst recognising the commonalities of their experiences. The clinical implications of the research findings are discussed including directions for future research.