Background Syphilis is caused by Treponema pallidum either via sexual exposure or vertical transmission during pregnancy. The disease course of infected individuals is divided into primary, secondary, and tertiary stages over a period of years. Latent syphilis most commonly involves the central nervous system and the aorta. Here we present a case of late latent syphilis presenting as heart block with evidence of myocardial fibrosis involving the septum and lateral wall in cardiac MRI. Case presentation A 53-year-old female patient, who was clinically diagnosed with late latent syphilis, presented with multiple episodes of syncopal attacks and was rushed to an outside hospital where ECG revealed a complete heart block. She was referred to our tertiary care centre. The patient was received in the Cardiac Care Unit and then referred for a cardiac MRI to identify a potential cause for the complete heart block. Recently published new Lake Louise criteria (nLLC) (Li et al. in Front Cardiovasc Med, 2021. https://doi.org/10.3389/fcvm.2021.739892), following the introduction of myocardial mapping, redefined imaging diagnosis according to the combined presence of a T1 criterion [presence of LGE (late gadolinium enhancement) or increased T1 mapping or extracellular volume values] and a T2 criterion (hyperintensity in T2 weighted STIR or increased T2 mapping values). Cardiac MRI features in our case were consistent with myocarditis based on the above criteria. Conclusions Myocarditis as a manifestation of late latent syphilis is very rare. Cardiac complications of late syphilis have so far been described in terms of ascending aortitis and dissection with coronary artery rupture. Syphilitic myocarditis occurs most commonly as a coincidental finding of endomyocardial biopsies. Targeted screening for involvement using CMR can be instrumental in elucidating this rare, but treatable diagnosis. We hereby report a rare case of myocarditis with heart block in a patient with late latent syphilis, hitherto unreported in the literature as of date.