Acute and early HIV infection (AEHI) is rarely diagnosed in sub-Saharan Africa, despite its potential contribution to incidence reduction. This qualitative study in Eswatini explored the experiences of health workers, people diagnosed with AEHI, and their partners towards AEHI diagnosis, to inform its scale-up. In-depth interviews were undertaken with 11 women and four men diagnosed with AEHI. Three patients' partners were interviewed about their understanding of AEHI and six health workers were interviewed about experiences of delivering AEHI services. Data were coded inductively and analysed iteratively following the principles of grounded theory. Experiences with AEHI diagnoses were shaped by (i) understanding the nature and consequences of AEHI, and (ii) social norms that influence disclosure and sexual behaviour. AEHI was a new concept for health workers who struggled to explain it to patients, leading to some confusion over their HIV status and misunderstandings around its high transmissibility and prognosis. Disclosure tended to occur to primary partners, if at all, limiting the ability to provide partner services, and one relationship breakdown was reported. If AEHI diagnosis and care interventions are to realise their full potential, it will be essential to reinforce the accompanying counselling sessions and closely monitor for potential social harms.