BackgroundPopulation ageing and access to anti-retroviral therapies in South Africa have resulted in ageing of the HIV/AIDS epidemic, which has implications for policy, planning and practice. Impactful interventions on HIV/AIDS for older persons require knowledge on effects of the pandemic on this population. A study was undertaken to assess knowledge, attitudes, and practices (KAP) of HIV/AIDS, as well as health literacy (HL) level of a population aged ≥ 50 years.MethodsA cross-sectional survey was conducted at three sites in South Africa and two sites in Lesotho with an educational intervention at the South African sites. At baseline, data were collected for assessment of KAP of HIV/AIDS and HL levels. The pre- and post-intervention comprised participants at South African sites being familiarised with the contents of a specially constructed HIV/AIDS educational booklet. Participants’ KAP was reassessed six weeks later. A composite score of ≥ 75% was considered adequate KAP and an adequate HL level.ResultsThe baseline survey comprised 1163 participants. The median age was 63 years (range 50–98 years); 70% were female, and 69% had ≤ 8 years’ education. HL was inadequate in 56% and the KAP score was inadequate in 64%. A high KAP score was associated with female gender (AOR = 1.6, 95% CI = 1.2–2.1), age < 65 years (AOR = 1.9, 95% CI = 1.5–2.5) and education level (Primary school: AOR = 2.2; 95% CI = 1.4–3.4); (High school: AOR = 4.4; 95% CI = 2.7–7.0); (University/college: AOR = 9.6; 95% CI = 4.7–19.7). HL was positively associated with education but no association with age or gender. The educational intervention comprised 614 (69%) participants. KAP scores increased post intervention: 65.2% of participants had adequate knowledge, versus 36% pre-intervention. Overall, younger age, being female and higher education level were associated with having adequate knowledge about HIV/AIDS, both pre- and post-intervention.ConclusionsThe study population had low HL, and KAP scores regarding HIV/AIDS were poor but improved following an educational intervention. A tailored educational programme can place older people centrally in the fight against the epidemic, even in the presence of low HL. Policy and educational programmes are indicated to meet the information needs of older persons, which are commensurate with the low HL level of a large section of that population.