BACKGROUND: Young adults living with HIV (YLWH) have suboptimal adherence to antiretroviral therapy (ART) and HIV care outcomes. Mobile health technologies are increasingly used to deliver interventions to address HIV health outcomes. However, not all YLWH have equal and consistent access to mobile technologies. METHODS: Using our novel Mobile Technology Vulnerability Scale (MTVS) to evaluate how vulnerable an individual feels with regard to their personal access to mobile technology in the past 6 months, we conducted a cross-sectional online survey with 271 YLWH (18-29 years) in the US to evaluate the relationships between MTVS and self-reported ART adherence. RESULTS: Participants reported changes in phone numbers (25%), stolen (14%) or lost (22%) phones, and disconnections of phone service due to non-payment (39%) in the past 6 months. On a scale of 0 to 1 (0 having no mobile technology vulnerability and 1 having complete mobile technology vulnerability), participants had a mean MTVS of 0.33 (SD =0.26). Black and financially constrained participants had the highest MTVS, which was significantly higher that other racial/ethnic and financially non-constrained groups, respectively. Higher MTVS was significantly associated with ART non-adherence and non-persistence. CONCLUSIONS: Findings suggest the need to measure MTVS to recognize pitfalls when using mobile health interventions and identify populations whose inconsistent mobile technology access may be related to worse health outcomes.