Introduction <p>Homelessness among older adults is an emerging social crisis in Iran, exacerbated by rapid population aging, inadequate welfare systems, and rising housing costs. Despite its growing prevalence, research on older homelessness in Iran remains limited. This study explores the lived experiences and underlying causes of homelessness among older adults to inform targeted prevention and intervention strategies.</p> Methods <p>A qualitative phenomenological design was employed to investigate life-course trajectories leading to homelessness. In-depth semi-structured interviews were conducted in 2025 with 27 homeless adults aged ≥ 60 years residing in municipal shelters in Tehran. Purposive and theoretical sampling ensured diversity across gender, duration of homelessness, and living arrangements. Data were analyzed using Colaizzi’s seven-step method. To ensure the trustworthiness of the findings, the study adhered to established qualitative criteria by addressing credibility, transferability, dependability, and confirmability through strategies such as member checking, maximum variation sampling, peer debriefing, and thick description.</p> Results <p>This study examined homelessness among 27 older adults (18 men, 9 women; mean age 65.5 years) living in Tehran shelters, most of whom had very low education and pension coverage, with shelter stays ranging from months to two decades. Analysis identified five interconnected categories driving their homelessness: economic-livelihood challenges (housing deprivation, financial crises, unstable work); family-generational factors (intergenerational poverty, conflict, and heightened gender vulnerability for women denied property rights or dependent on unreliable children); harmful exposures (childhood trauma, addiction, violence, high-risk lifestyles, and health incapacitation); individual factors (self-perceived life choices and skill deficits); and institutional-support failures (inadequate pensions, weak welfare systems, and the collapse of traditional family support networks). These factors converged into two distinct pathways into homelessness: a gradual trajectory stemming from lifelong cumulative disadvantage, and a rapid onset triggered by acute old-age crises such as spousal death, severe illness, or sudden housing cost inflation.</p> Conclusion <p>Older homelessness in Iran emerges through cumulative disadvantage across the life course, with distinct gendered pathways. Practical interventions must include: structural reforms in housing affordability and pension systems, particularly for informal workers; [<CitationRef CitationID="CR2">2</CitationRef>] gender-sensitive policies addressing women’s property rights and men’s addiction treatment needs; life-course preventive strategies beginning in childhood to disrupt intergenerational poverty cycles; and integrated service models combining healthcare, social support, and housing assistance specifically designed for older homeless adults.</p>