BACKGROUND: There is high post-hospital discharge mortality among persons with HIV who are hospitalized, and post-hospital survival is strongly associated with early HIV clinic linkage, clinic attendance, and antiretroviral therapy adherence. The Daraja intervention, a context-tailored case management strategy implemented and tested through a randomized trial in Tanzania, was associated with improved HIV clinic linkage, retention, and ART initiation and adherence. METHODS: We conducted in-depth interviews (IDIs) in a sub-sample of 40 study participants (20 control and 20 intervention) 12 months after enrollment into the trial to gain an in-depth understanding of the barriers to HIV care engagement and the perceived mechanisms through which the Daraja intervention impacted these barriers. We also conducted IDIs with 20 health care providers. We used a thematic analysis approach to generate themes following the Gelberg-Andersen behavioral model for vulnerable population domains. RESULTS: Perceived stigma, coupled with the mistrust of healthcare providers, underemployment or lack of reliable income, unreliable transport, and a lack of social support, were identified as key barriers to HIV clinic attendance and ART adherence. Perceived stigma complicated not only linking to and attending an HIV clinic but also decision-making regarding the choice of the clinic's location. The Daraja intervention was reported to help normalise HIV diagnosis, plug the social support gap, increase patients' self-efficacy and their capacity of participants to navigate the HIV clinic during HIV clinic linkage. CONCLUSION: These qualitative research results identified several important barriers to engaging in HIV care and provide insights into the mechanisms through which the Daraja intervention operated to affect the perceived stigma, social support, self-efficacy, and increased capacity of participants to navigate the HIV clinic during HIV clinic linkage. DARAJA TRIAL REGISTRATION: ClinicalTrials.gov, NCT03858998. Registered on 01 March 2019.