Patient costs are a critical barrier to the elimination of mother to child HIV transmission. Despite the Ugandan government providing free public HIV services, infant antiretroviral (ARV) prophylaxis coverage remains low (25%). To understand costs mothers incur in accessing ARV prophylaxis for their infants, we conducted a mixed methods study to quantify and identify their direct costs. We used cross-sectional survey data and focus group discussions from 49 HIV-positive mothers in Uganda. Means and standard deviations were calculated for the direct costs (e.g., transportation, caretaker, services/medications) involved in accessing infant HIV services. The direct cost of attending HIV clinic visits averaged $3.71 (SD = $3.52). Focus group discussions identified two costs hindering access to infant HIV services: transportation costs and informal service charges. All participants reported significant costs associated with accessing infant HIV services - the equivalent of 2-3 days' income. To address transportation costs, community and home care models should be explored. Additionally, stricter policies and oversight should be implemented to prevent informal HIV service charges.