Introduction Mitochondria play a central role in antiviral defense, and SARS-CoV-2 proteins modulate this response by interacting with mitochondrial components. Viral infection also affects the host regulome, particularly microRNA (miRNA) activity [1,2]. Two mitochondrial-encoded miRNAs, hsa-miR-4485-3p and hsa-miR-4485-5p, derived from 16S mitochondrial RNA, are known to be dysregulated during stress, including viral infections [3,4]. This study evaluated their expression in serum from COVID-19 patients with varying disease severity compared to healthy controls. Material and methods Serum samples were collected from 52 COVID-19 patients (13 hospitalized, 13 in intensive care units [ICU]), 13 convalescents, and 13 controls. Total RNA was extracted and miRNA levels quantified by RT-qPCR, with hsa-miR-103a-3p as reference. Results Expression of hsa-miR-4485-5p and hsa-miR-4485-3p was significantly reduced in hospitalized patients (ANOVA, p < 10⁻⁴). Specifically, hsa-miR-4485-5p showed Ct means of 33.75 (patients) versus 28.16 (controls), while hsa-miR-4485-3p showed 39.19 (patients) versus 29.87 (controls). Both miRNAs were markedly lower in ICU and hospitalized patients compared to convalescents and controls (p < 0.05). The reference miRNA also differed modestly, indicating overall reduced circulating miRNA levels in COVID-19. Notably, hsa-miR-4485-3p demonstrated significant associations with severity, supporting its potential role as a biomarker for COVID-19 progression.