BACKGROUND: Antiretroviral therapy (ART) use by people living with HIV reduces HIV transmission, morbidity, mortality, and improves quality of life. Good ART adherence is required to achieve these benefits. We investigated how the environmental, social, economic and behavioural experiences of people living with HIV with poor viral suppression could explain their non-adherence to long term ART. METHODS: This qualitative cross-sectional study was conducted in Uganda between September 2015 and April 2016. Thirty individuals on ART for 5 years or more (10 on first line and 20 on second line), with poor viral suppression, were randomly selected from a cohort of people living with HIV on ART. In-depth interviews about ART; awareness, adherence counselling, obstacles to daily adherence and regimen switches were conducted. Emerging themes from the interviews transcripts and field notes were identified and thematic content analysis done. Participants' consent, compensation, confidentiality and study ethical approvals were ensured. RESULTS: We found that poor adherence to long term ART was due to: travel for work or social activities, stigma, receiving little or no continuous ART adherence education, alcohol consumption and use of alternative 'HIV cure' medicines. Other reasons included; ART side effects, treatment fatigue, belief that long-term ART or God can 'cure HIV', and food security. CONCLUSIONS: Achieving optimal ART benefits requires continuous provision of ART adherence education to individuals on long term ART. This helps them overcome the challenges related to living with HIV: worries of food insecurity, alcohol misuse, economic hardship, and beliefs in HIV cures and use of unproven alternative HIV treatments. People living with HIV who travel require adherence support and larger quantities of ART refills to cover their time away.