Abstract Background Cardiovascular disease (CVD) in people living with HIV (PLWH) remains poorly understood, and the profile of disease differs between high-income and low- and middle-income settings[1]. Subclinical cardiovascular abnormalities may be present at the time of HIV diagnosis and serve as potential substrate for future CVD[2]. Biochemical markers are fundamental in cardiac evaluation, and various novel assays have recently been discovered. Purpose To assess the presence and evolution of subclinical myocardial disease, we prospectively assessed the hearts of newly diagnosed PLWH and matched, HIV-uninfected controls using cardiac biomarkers and correlated our findings with cardiovascular magnetic resonance imaging (CMR). Methods Newly diagnosed, antiretroviral treatment (ART) naïve PLWH were recruited along with HIV uninfected, age- and sex-matched controls in the Western Cape Province of South Africa. All participants underwent measurement of high-sensitivity cardiac troponin T (hs-cTnT), N-terminal pro-B-type natriuretic peptide (NT-proBNP), soluble ST2 (sST2), Galectin-3, and a CMR study with multiparametric mapping. The HIV group started ART and was re-evaluated 9 months later. The cardiac biomarkers and their correlation with CMR parameters were evaluated in, and between groups. Results Compared with controls (n=22), hs-cTnT (4.0 ng/l vs 5.1 ng/l; p=0.004) , NT-proBNP (23.2 ng/l vs 40.8 ng/l; p=0.02), and Galectin-3 (6.8 ng/ml vs 9.0 ng/ml; p=0.002) were all significantly higher in the ART naïve group (n=73). After 9 months of ART, hs-cTnT (5.1 ng/l vs 4.3 ng/l; p=0.02) and NT-proBNP (40.8 ng/l vs 28.5 ng/l; p=0.03) both decreased significantly, and a trend of decrease was seen in sST2 (16.5 ng/ml vs 14.8 ng/l; p=0.08). Galectin-3 did not demonstrate decrease over time (9.0 ng/ml vs 8.8 ng/ml; p=0.6). The cardiac biomarkers that showed the best correlation with CMR measurements native T1, T2, and ECV, were NT-proBNP (rs≥0.4, p<0.001) and Galectin-3 (rs≥0.3, p<0.01). Conclusion Our cardiac biomarker data supports the presence of subclinical myocardial injury, remodelling, and fibrosis at HIV diagnosis and ART had a positive influence on these blood markers. It remains unclear if the underlying pathological processes were fully addressed by ART. The elevation of Galectin-3 despite ART may be indicative of ongoing cardiac remodelling that may incur future risk of CVD, and necessitates further study. The ability of cardiac biomarkers to detect and track tissue abnormalities diagnosed with CMR, showed promise. With additional research, this could lead to improvements in screening and monitoring myocardial abnormalities, even in CMR-limited settings.