OBJECTIVES: To examine cognitive beliefs associated with hoarding in the context of homelessness, focusing on fear of future material deprivation, and to compare housing-related adversities across groups with hoarding difficulties, homelessness or both. DESIGN: Cross-sectional, three-group comparative study. METHODS: Adults in the UK/Ireland were recruited between July 2023 and April 2024 through third-sector and clinical partners via online, postal and in-person routes. Participants were grouped as hoarding difficulties with homelessness in the past 10 years (H&H; n = 47), hoarding difficulties without homelessness (HD; n = 43) and homelessness without hoarding difficulties (HM; n = 39). Hoarding difficulties were identified by professional referral and eligibility screening, mapping onto DSM-5 criteria (self-report endorsement of all criteria). Primary outcomes were Beliefs About Hoarding Questionnaire-Revised (BAH) subscales (fear of material deprivation, harm avoidance, attachment disturbance). Secondary outcomes included negative housing experiences, hoarding severity (SI-R), depression (PHQ-8), anxiety (GAD-7), functioning (WSAS) and early material deprivation (EEMD). Mixed-model ANOVA tested group differences in BAH subscales, and Kruskal-Wallis tested housing experiences. RESULTS: A significant group-by-belief interaction emerged. Fear of material deprivation and attachment disturbance were higher in H&H and HD than in HM. Harm avoidance was highest in H&H. H&H reported more negative housing experiences than HD and did not differ from HM (H&H ≈ HM > HD). Exploratory analyses showed higher depression, anxiety and impairment in H&H. HD showed the greatest hoarding severity (SI-R total, clutter, discarding), whereas excessive acquisition was similar in H&H and HD. CONCLUSIONS: Hoarding difficulties in homelessness contexts appear embedded in cumulative psychosocial vulnerability rather than explained by deprivation alone. Harm avoidance may be particularly salient when hoarding co-occurs with homelessness, suggesting potential targets for formulation and intervention in homelessness services.