Subjective wellbeing was examined amongst 274 adults living with HIV in Australia and the United States of America. There were 164 adults aged 49 years and under, and 110 adults aged 50 years and over. Participants completed a composite questionnaire comprising the Personal Wellbeing Index-Adult (PWI-A), the HIV-Unsupportive Social Interactions Inventory (USII), and demographic and health-related items. Participants reported mean PWI-A scores of 54.7 points, considerably below the Western population normative range of 70–80 points. Older adults reported significantly greater subjective wellbeing compared to younger adults, but still below the normative range. Experiences of unsupportive social interactions were a significant predictor of reduced subjective wellbeing amongst all participants. Qualitative comments provided a greater understanding of the characteristics and psychological devices that enable some older adults to maintain and/or increase subjective wellbeing, even in the face of negative stressors such as unsupportive social interactions. This provides valuable information for service providers and clinicians as HIV increasingly becomes recognised as a disease affecting older adults in developed nations. Rather than positioning the ageing HIV-population as a potential burden, it is proposed that learning more about the coping mechanisms employed by older adults with HIV could prove beneficial for the HIV-population as a whole.