BACKGROUND: Mental health is linked to HIV outcomes, including linkage into care and adherence to medication. Integrated care for mental and physical health is recommended. HIV testing and counselling sessions represent an opportunity to implement interventions to address mental health, however it is first necessary to understand the roles, current practice, knowledge and attitudes of the testing and counselling staff. METHODS: This qualitative study used semi-structured interviews with HIV testing and counselling staff at four centres of a HIV healthcare provider charity in Uganda. Interviews focused on their current practice, perceptions of mental health and their role in supporting this, challenges of this work, training and support needs, and views of potential greater emphasis on mental health work in their role. Data were audio-recorded, transcribed verbatim, and analysed thematically. RESULTS: Data from twenty-one testing and counselling staff revealed five themes. Clients presented to counselling staff with needs spanning bio-psycho-social domains, where psychological health was intertwined with HIV management, medication adherence, and seen as "inseparable" from HIV itself. Mental health was largely thought about as "madness", identifiable from extreme behaviour. As such, common mental health problems of anxiety and depression were not often seen as part of mental health. Approaches to intervening with mental health were seen as behavioural, with some ideas about changing thinking styles. Participants demonstrated significant practice of common techniques to address mental health. Needs were identified for further training in suicide risk assessment and identification of depression, together with greater clinical supervision. Participants described significant conflict within their roles, particularly balancing time demands and need to achieve testing targets against the need to offer adequate mental health support to clients in need. CONCLUSIONS: HIV testing and counselling staff described a diverse role that already includes addressing mental health. Mental health is "vital" to their work, however the time needed to address it is at odds with current testing targets. They require more training and resources to effectively address mental health, which is vital to optimising HIV outcomes. Interventions to integrate mental health support into HIV testing and counselling sessions need to be further researched and optimised.