Late HIV treatment remains a global public health issue despite significant efforts. To better understand what shapes this issue, we interviewed 36 Vietnamese ART-naive patients who came to HIV treatment in 2017. Half of them had intake CD4 counts fewer than 100 cells/mm 3 , the others had intake CD4 counts of 350 cells/mm 3 and above. Late diagnosis was the reason of late treatment in our sample. Most late presenters were not members of the key populations at increased risk of HIV (e.g., people who inject drugs, commercial sex workers, and men who have sex with men). Individual-level factors included low risk appraisal, habit of self-medication, and fear of stigma. Network and structural-level factors included challenges to access quality health care, normalization of HIV testing in key populations and inconsistent provider-initiated HIV testing practices. Structural interventions coupled with existing key population-targeted strategies would improve the issue of late HIV diagnosis.