The herb thyme (Thymus vulgaris) has multiple therapeutic uses. In this study, we explored how T. vulgaris leaf extract protects liver cells against sodium nitrite-(NaNO2) induced oxidative stress. Mice were divided into four groups; each group received one of the following treatments orally: saline; T. vulgaris extract alone; NaNO2 alone; or T. vulgaris extract + NaNO2. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), reduced glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), IL-1β, IL-6, TNF-α, and total proteins were measured in serum using standard methods. TNF-α, hemooxygenase-1 (HO-1), thioredoxin, SOD, and GSH synthase, all of which are linked to oxidative stress, were measured using quantitative real-time PCR (qRT-PCR). In mice treated with T. vulgaris extract, the effect of NaNO2 on ALT and AST levels and total proteins was reduced, and its effect on antioxidant levels was reversed. Normally, NaNO2 causes hepatocyte congestion and severe hepatic central vein congestion. Tissues in the mice treated with T. vulgaris were restored to normal conditions. Our results demonstrate that NaNO2- induced hepatic injury is significantly reduced by pretreatment with T. vulgaris extract, which protects against hepatic oxidative stress and its associated genes at the biochemical, molecular, and cellular levels.