Essential hypertension (EH) is a multifactorial disease. Interferon-γ (IFN-γ) plays an important role in the onset of EH through cytokine-mediated systemic inflammatory responses. We aimed to determine whether the methylation status of the IFN-γ gene (IFNG) promoter is involved in the pathogenesis of EH. Six copies of CpG dinucleotides are distributed between 3,203 bp and 3,121 bp upstream from the transcription initiation site of IFNG, termed CpG1 to CpG6 in the 5′-to-3′ direction. We recruited 96 patients with EH and 96 sex- and age-matched healthy subjects as controls. Using bisulfate pyrosequencing datasets, we analyzed the methylation status of the six CpG sites and thus found that CpG5 was consistently methylated in all of the 96 EH patients and 96 control subjects. Among the remaining five CpG sites, there was no significant difference in the methylation levels of CpG4 and CpG6 between the two groups. By contrast, CpG1 (P = 0.003) and CpG3 (P = 5.87 × 10⁻⁷) were highly methylated among the EH subjects compared with the controls, whereas CpG2 (P = 1.24 × 10⁻¹²) was significantly less methylated in among EH subjects. The methylation levels of CpG2 were still lower after adjustment with logistic regression (adjusted P = 0.032). The CpG2 methylation level was an effective marker of EH (area under curve = 0.384; P = 1.40 × 10⁻¹⁵). The present study shows that hypomethylation of the IFNG promoter is significantly related to the risk of EH, providing new insights into the pathogenesis of EH.