The chronic illness trajectory and its outcomes are well explained by the concept of illness identity; the extent to which ill individuals have integrated their diagnosed chronic illness into their identity or sense of self. The capacity to measure illness identity in people living with HIV (PLHIV) is still relatively unexplored. We explored the cross-cultural adaptation of a Belgian developed Illness Identity Questionnaire (IIQ) and validated the instrument using a sample of South African adults living with HIV. We followed a phased scale adaptation and validation process which included an investigation of conceptual, item and semantic equivalence. This was undertaken to assess relationship, meaning, acceptance and relevance of the illness identity construct, its latent factors and items in the South African context. For operational equivalence we evaluated whether the format, instructions and mode of administration of the IIQ could be maintained as in the original context. Lastly, we examined the psychometric properties of the IIQ. The concept of illness identity in PLHIV, was found relevant within this context. Five items from the original IIQ were excluded from the adapted IIQ due to either semantic insufficiency and/or inadequate measurement equivalence. The mode of administration of the IIQ was amended for the context. The original four factor 25-item model did not fit current data, however, a better contextualized, four-factor, 20-item model was identified and found valid in the current setting. The results showed adequate statistical fit; χ2/d.f. = 1.516, RMSEA = .076, SRMR = .0893, and CFI = .909. Convergent and discriminant validity were also tenable. The cross-cultural adaptation and validation of the IIQ was successful, resulting in the availability of an instrument capable of measuring illness identity in PLHIV in a high HIV prevalence and resource-constrained setting. This therefore addresses the paucity of information and expands on knowledge about illness identity.