Homelessness is a complex social issue that is of increasing concern to most developed nations.Homelessness is more than not having a house; it is a form of social exclusion and carries significant physical, psychological, and social challenges. The broad aim of the current thesis was to investigate how the psychological and social aspects of the homeless experience can influence outcomes, such as well-being. In particular, the research focuses on processes related to social categories, social identities, and social support of people, as people transition through homeless accommodation services.The first empirical chapters (Chapter 4 and 5) focus on the impact of self-categorization as homeless. Study 1 (Chapter 4) was a qualitative and quantitative cross-sectional study with 119 residents of homeless accommodation services in South-East Queensland. Results demonstrated that while the majority of participants accepted the homeless label (55%), a large portion of residents (31%) rejected the homeless label, or were ambivalent (14%). Respondents who rejected the homeless label reported greater personal well-being and lower negative mood symptoms than participants who accepted the label. Study 2 (Chapter 5) explored this further using an experimental paradigm among 80 residents of a homeless service. Participants who were required to selfcategorize as homeless at the beginning of the questionnaire had significantly lower future life aspirations and perceived competency than participants who did not. Further, future life aspirations and perceived competency both mediated the relationship between self-categorization and wellbeing.Studies 3 and 4 (Chapters 6 and 7) focus on social identity processes for people transitioning through homelessness. Study 3 assessed how multiple group memberships and service identification related to well-being and positive housing outcomes among 76 participants while they were residing in a homeless accommodation service and again 2 -4 weeks after leaving the service (or three months later if participants had not left the service). The results found that multiple group memberships and service identification independently predicted well-being at Time 2, via social support. Both social identity processes also indirectly predicted housing outcomes via social support. Study 4 built on this research by exploring the antecedents and outcomes that are related to service identification among 296 residents across 19 services. Characteristics of the service delivery model and perceptions of discrimination predicted participants' identification with staff. Further, identification with staff predicted service engagement 6 months later and identification with residents predicted joining new groups 6 months later.The final study (Chapter 8) examined how one of these social processes, namely the relationship between social support and well-being, related to an "individual" trait -emotion iii regulation. Results from a one-year longitudinal study, conducted over three time-points, supported a bi...