In folk medicines, Justicia gendarussa (J. gendarussa) is used as a depurative herb for treating fever, pain, and cancer and as laxative for constipation. The aim of the present investigation was to evaluate the hepatoprotective effect of the leaf methanol extract of J. gendarussa leaf (J gMe) against carbofuran (CF)-intoxicated liver injuries in Sprague−Dawley rats, along with the antioxidant activity of this extract. For this purpose, levels of serum diagnostic markers, hepatic antioxidant enzymes, and liver histoarchitecture were employed to justify the protective efficacy of J gMe. In addition, the phenolic and flavonoid contents of the extract were quantified, and antioxidant activity was investigated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide, hydrogen peroxide, and hydroxyl free radical scavenging assays. Results revealed that the leaf extract caused a significant (<0.05, <0.01) decrease of the level of hepatic enzymes, triglycerides, and bilirubin and an increase of the total protein. J gMe has also significantly (<0.05, <0.01) lowered the level of malonylaldehyde. Carbofuran markedly suppressed hepatic antioxidant enzymes, however, the leaf extract significantly augmented these enzymes. The hepatoprotective effect was demonstrated by the improvement in the histo-architectural features of liver sections of CFintoxicated rats treated with J gMe at 500 mg/kg dose. In addition, J gMe showed moderate total phenolic and total flavonoid content, whereas the IC 50 values of DPPH, nitric oxide, hydrogen peroxide, and hydroxyl free radical scavenging assays were 71.31 ± 0.42, 134.82 ± 0.14, 47.69 ± 0.38, and 118.44 ± 0.30 μg/mL, respectively. In conclusion, the present study suggests the protective role of J gMe against hepatic injury induced by CF, which may be attributed to its higher antioxidant properties and thereby scientifically justifies its traditional use.