The cardioprotective effects of antiretroviral treatment (ART) in adolescents with perinatal HIV infection (APHIV) may depend on age at ART initiation. We used cardiovascular magnetic resonance (CMR) to characterize and compare residual cardiac changes in apparently healthy APHIV with early and delayed ART initiation compared to sex- and age-similar HIV uninfected peers. We defined early and delayed ART as, respectively, treatment initiated at <5 years and ≥5 years of age. Cardiac function, mechanical deformation, geometry and tissue composition were assessed. APHIV had distinct albeit subclinical cardiac phenotypes depending on timing of ART initiation. For example, changes in early ART suggested comparatively worse diastology with preserved systolic function while delayed ART was associated with comparatively increased diffuse fibrosis and LV dilatation with reduced systolic function. The long-term clinical significance of these changes remains to be determined.