Background. Recent studies suggest that infection with human T-lymphotropic virus 1 (HTLV-1) might be associated with bronchiectasis among Indigenous Australians. The present study compared the clinical characteristics and outcomes of bronchiectasis in this population, according to HTLV-1 serologic status. Methods. We performed a retrospective cohort study of Indigenous adults with bronchiectasis and known HTLV-1 serologic status admitted to Alice Springs Hospital, central Australia, from January 2000 through December 2006. Results. Among 89 Indigenous adults whose HTLV-1 serologic status was confirmed, 52 (58.4%) were HTLV-1 seropositive. Differences between HTLV-1-seropositive and HTLV-1-seronegative groups were apparent in childhood presentations and adult outcomes. Among adults, an increasing number of bronchiectatic lobes (univariable odds ratio [OR], 1.51; 95% confidence interval [CI]; 1.03-2.20; P =. 033) and the presence of ground-glass opacities at chest high-resolution computed tomography (univariable OR, 8.54; 95% CI, 1.04-70.03; P =. 046) predicted HTLV-1 infection. Cor pumonale (HTLV-1-positive group, 10/52; HTLV-1-negative group, 1/37; P =. 023) was more frequent among HTLV-1-seropositive adults, who also experienced a higher disease-specific mortality (univariable OR, 5.78; 95% CI, 1.17-26.75; P =. 028). Only HTLV-1-seropositive patients were admitted specifically for the treatment of infected skin lesions, and this finding predicted death (multivariable OR, 6.77; 95% CI, 1.46-31.34; P =. 014). Overall mortality was high; 34.2% of the cohort died at a median age of 42.5 years. Conclusions. HTLV-1 infection contributes to the risk of developing bronchiectasis and worsens outcomes among Indigenous Australians.