Prevalence of HIV after age 50 is considerable, especially in southern Africa. Negative social constructions of HIV in older age, and the health consequences of ageing with the virus, mean that having HIV presents a challenge for many people's roles and social memberships, threatening to disrupt their sense of self. Using constructivist grounded theory and qualitative data from rural Malawi, this paper describes how older men and women deal with these identity challenges. Drawing on a symbolic interactionist framework, it uses identity control theory to explore how the study's participants presented their post‐diagnosis behaviours in ways that maintained their most significant pre‐diagnosis identities as ‘adults’, a label they gave to the core identity of being a person who belongs in the social world. Considering the processes through which older people with HIV navigated challenges to their identities in light of the intersectional influences of HIV and age‐related stigma and illness, provides insight into how older people might experience HIV, as well as informing theoretical understandings of identity formation and maintenance in light of chronic and/or stigmatising illness more broadly.