Abstract Background Patients with a significant decrease in hepatic venous pressure gradient (HVPG) have a considerable reduction of liver complications and higher survival after HCV eradication. Objectives To evaluate the association between the baseline blood microbiome and the changes in HVPG after successful direct-acting antiviral (DAA) therapy in patients with HCV-related cirrhosis. Methods We performed a prospective study in 32 cirrhotic patients (21 HIV positive) with clinically significant portal hypertension (HVPG ≥10 mmHg). Patients were assessed at baseline and 48 weeks after HCV treatment completion. The clinical endpoint was a decrease in HVPG of ≥20% or HVPG <12 mmHg at the end of follow-up. Bacterial 16S ribosomal DNA was sequenced using MiSeq Illumina technology, inflammatory plasma biomarkers were investigated using ProcartaPlex immunoassays and the metabolome was investigated using GC-MS. Results During the follow-up, 47% of patients reached the clinical endpoint. At baseline, those patients had a higher relative abundance of Corynebacteriales and Diplorickettsiales order, Diplorickettsiaceae family, Corynebacterium and Aquicella genus and Undibacterium parvum species organisms and a lower relative abundance of Oceanospirillales and Rhodospirillales order, Halomonadaceae family and Massilia genus organisms compared with those who did not achieve the clinical endpoint according to the LEfSe algorithm. Corynebacteriales and Massilia were consistently found within the 10 bacterial taxa with the highest differential abundance between groups. Additionally, the relative abundance of the Corynebacteriales order was inversely correlated with IFN-γ, IL-17A and TNF-α levels and the Massilia genus with glycerol and lauric acid. Conclusions Baseline-specific bacterial taxa are related to an HVPG decrease in patients with HCV-related cirrhosis after successful DAA therapy.