The COVID-19 pandemic and associated prevention strategies caused widespread interruptions to care and treatment for people living with HIV. Adolescents living with HIV (AWHIV) were particularly vulnerable to poor mental and physical health during COVID-19. We assessed the burden of generalized and COVID-19–related anxiety and associations with adherence to HIV care and treatment and viral load suppression (VLS) among AWHIV during the peak of the COVID-19 pandemic in Tanzania. Methods This cross-sectional study was conducted among AWHIV aged 15–19 years attending 10 clinics in Dar es Salaam from April 2022-February 2023. Study participants completed a self-administered questionnaire including Generalized Anxiety Disorder (GAD), COVID-19-related anxiety, and other psychosocial and physical health and support measures. HIV visit adherence, viral load and sociodemographic data were abstracted from patient health records. Analysis: Multivariable (MV) quasibinomial and logistic regression models examined associations of Generalized and COVID-19-related anxiety with visit adherence and HIV virologic suppression (HIV VL < 50 copies/mL). Data were analyzed using R software. Results 658 AWHIV (52% male) were included in this analysis. Most (86%) had been on antiretroviral treatment (ART) for at least four years, 55% attended at least 75% of their scheduled clinic visits, and 78% were HIV virologically suppressed. The median GAD and COVID-19-related anxiety scores were 2 (IQR: 0–5, and 26 (IQR: 13–43; respectively. Only 2% scored moderate-severe generalized anxiety (score 10–21). We found no significant associations between COVID-19-related anxiety or GAD and visit adherence. Higher GAD was inversely associated with VLS (adjusted odds ratio (AOR): 0.89 (95% CI 0.81, 0.98)). Female gender and higher quality of physical life were significantly associated with VLS. Conclusion. Low levels of generalized and COVID-19 related anxiety were reported among Tanzanian AWHIV. Integrating screening and management of generalized anxiety screening into HIV care for AWHIV could improve VLS among this population.