Kaposi sarcoma (KS) is a serious AIDS-defining malignancy that can progress rapidly in the setting of profound immunosuppression. Non-adherence to antiretroviral therapy (ART) remains a major barrier to viral suppression, particularly among underserved populations. We present the case of a 36-year-old African American man who has sex with men (MSM), living in an underserved community, with a history of HIV/AIDS and late latent syphilis. The patient developed disseminated KS after six months of non-adherence to bictegravir/emtricitabine/tenofovir alafenamide (Biktarvy). He presented with a CD4 count of 44 cells/µL and a viral load of 592,000 copies/mL. Clinical findings included multiple violaceous skin lesions, pulmonary reticulonodular infiltrates with pleural effusion, and lymphadenopathy. Biopsy confirmed KS. He was restarted on ART and prophylactic antibiotics upon discharge. This case highlights the severe consequences of ART non-adherence in a vulnerable population. Targeted interventions, including long-acting ART, behavioral support, and telehealth innovations, are essential to improve retention in care and prevent advanced HIV-related complications like KS.