Presepsin, a cleaved peptide of soluble CD14, may become a promising biomarker for assessing disease severity and mortality in coronavirus disease 2019 (COVID-19). Patients with severe COVID-19 frequently develop bacterial and fungal superinfections, as well as herpes simplex virus-1 (HSV-1) reactivation, which may exacerbate disease progression. This study aimed to evaluate the impact of concomitant infections on serum presepsin levels. Serum presepsin levels were measured using an enzyme-linked immunosorbent assay (ELISA) in 63 patients with moderate COVID-19, 60 patients with severe disease, and 49 healthy controls. Correlations with procalcitonin and the presence of superinfections or HSV-1 reactivation were assessed. Consistent with previous studies, serum presepsin levels were the highest in patients with severe COVID-19 (p = 0.002 compared to patients with moderate disease). Within this group, non-survivors exhibited significantly elevated presepsin levels (p = 0.027). A positive correlation between presepsin and procalcitonin was observed in both moderate and severe COVID-19 cases. Patients with bacterial or fungal superinfections showed presepsin levels comparable to those without secondary infections. However, presepsin levels were markedly elevated in patients with HSV-1 reactivation (p = 0.002). After excluding patients with HSV-1 reactivation, presepsin levels no longer differed between moderate and severe COVID-19 cases, though they remained higher than in healthy controls (p < 0.001 for both comparisons). In conclusion, these findings suggest that elevated serum presepsin levels in severe COVID-19 are primarily driven by HSV-1 reactivation rather than bacterial or fungal superinfections.