Adult T-cell leukaemia/lymphoma (ATLL) is a rare, aggressive haematological malignancy linked to human T-cell leukaemia virus type I (HTLV-1) and associated with poor outcomes. Despite its higher prevalence in HTLV-1-endemic regions, the relationship between clinical characteristics and patients' sociocultural background remains underexplored. We retrospectively analysed 79 ATLL patients treated at our institution (1993-2023). The median age at diagnosis was 47 years, and 72% of patients were of Caribbean origin. Median progression-free and overall survival were 10.2 and 16.2 months, respectively, with only five patients receiving allogeneic stem cell transplantation. Central nervous system (CNS) involvement at diagnosis occurred in 22% of patients and was associated with worse outcomes, while 14% experienced CNS relapse within a median of 4.9 months. Using the Ontario Marginalization Index, we found higher levels of material, household/dwelling and racialized/newcomer-related marginalization compared to the general Greater Toronto Area population, though these factors were not linked to poorer outcomes. Our findings reveal that ATLL patients in this cohort were predominantly of Caribbean descent, presented at a young age and faced significant CNS involvement and poor survival outcomes, underscoring ATLL as an unmet clinical need.