Background: Perinatally HIV-infected adolescents (PHIVA) are exposed to a chronic systemic infection and long-term antiretroviral therapy (ART), leaving them susceptible to morbidities associated with inflammation, immunodeficiency, and drug toxicity. Methods: Data collected 2001-2016 from PHIVA aged 10-19 years within a regional Asian cohort were analysed using competing risk time-to-event and Poisson regression analyses to describe the nature and incidence of morbidity events and hospitalisations, and identify factors associated with disease-related, treatment-related, and overall morbidity. Morbidity was defined according to WHO clinical staging criteria and US National Institutes of Health Division of AIDS criteria. Results: A total 3,448 PHIVA contributed 17,778 person-years. Median age at HIV diagnosis was 5.5 years and ART initiation was 6.9 years. There were 2,562 morbidity events and 307 hospitalisations. Cumulative incidence for any morbidity was 51.7% and hospitalisation was 10.0%. Early adolescence was dominated by disease-related infectious morbidity, with a trend toward non-infectious and treatment-related morbidity in later adolescence. Higher overall morbidity rates were associated with a CD4 count <350 cells/μL, HIV viral load ≥10,000 copies/mL, and experiencing prior morbidity at age <10 years. Lower overall morbidity rates were found for those aged 15-19 years compared to 10-14 years, and those who initiated ART at age 5-9 years compared to <5 or ≥10 years. Conclusions: Half of our PHIVA cohort experienced a morbidity event, with a trend from disease-related infectious events to treatment-related and non-infectious events as PHIVA age. Antiretroviral therapy initiation to prevent immune system damage, optimise virologic control, and minimise childhood morbidity are key to limiting adolescent morbidity.