Introduction: Thyroid disorders are known to be a risk factor for cardiovascular diseases. Epicardial fat thickness (EFT) and oxidative stress are also believed to be major risk factors for cardiovascular events. The aim of this study was to evaluate the possible relationship between oxidative stress parameters and EFT in patients with subclinical hypothyroidism (SCH). Material and methods: A total of 60 individuals (30 patients with SCH and 30 healthy controls) were recruited for the study. The EFT and oxidative stress parameters of all participants were analyzed at baseline; the same were analyzed in SCH patients after achievement of a euthyroid state. Results: Compared to healthy subjects, SCH patients had significantly higher EFT and oxidative stress parameters (p < 0.05 for all). EFT and oxidative stress parameters both decreased after treatment, but only the decrease of EFT levels was statistically significant after thyroid hormone replacement (p < 0.05). Serum EFT levels were not significantly correlated with oxidative stress index (r = 0.141, p = 0.458). Conclusions: Previous studies have demonstrated that visceral adipose tissue and oxidative stress are major risk factors for cardiovascular events; our study demonstrated that EFT, a visceral adipose tissue, and oxidative stress parameters were higher, and could be used as an indicator for cardiovascular diseases in patients with SCH.