HIV knowledge may impact patient access, understanding, and utilization of HIV medical information. This study explored the relationship between personal HIV knowledge, appointment adherence and treatment outcomes. HIV-infected individuals (n = 210) were assessed on factors related to HIV knowledge and appointment adherence. Adherence data and laboratory values were extracted from medical records. HIV knowledge was measured by participants' knowledge of their CD4 count and viral load (VL) and adherence was defined as attendance at >75 % of appointments. Two-thirds of participants were adherent, but only one-third knew their CD4 count and VL. Controlling for time since last appointment, HIV knowledge more than doubled the odds of appointment adherence. In combination with relationship with provider, knowledge predicted increased CD4 count and increased odds of an undetectable VL by almost five times. Personal HIV knowledge may be a valuable indicator of engagement in care and may also facilitate improved treatment outcomes.