Abstract <p>Hydrogen sulfide (H₂S) has emerged as a critical signaling molecule in plants, particularly under stress conditions. This study investigates the role of exogenous H₂S at two levels of 100 and 200 μM, supplied as sodium hydrosulfide (NaHS), in enhancing the antioxidant defense and biochemical resilience of <i>Lavandula angustifolia</i> Miller subjected to 0, 150 and 300 mM NaCl stress for 7 and 14 days. The experiments were designed to evaluate key physiological parameters including malondialdehyde (MDA)and Hydrogen peroxide (H₂O₂) contents as well as antioxidant enzymes activity, ionic balance (Na⁺, Cl⁻, and K⁺ content), hydrogen sulfide (H₂S) and protein levels across different treatments. Results demonstrated that NaHS treatment could effectively alleviate oxidative damage caused by salt stress and reduce the accumulation of MDA and H₂O₂ through enhancing the activities of antioxidant enzymes. The highest antioxidant activity was observed in plants treated with either 0 mM NaCl + 200 μM NaHS or 300 mM salt stress with 100 μM NaHS, highlighting the dual role of H₂S in modulating the plant’s response to varying stress levels. Additionally, the treatment of 150 mM NaCl combined with NaHS application significantly increased H₂S content, which in turn enhanced antioxidant capacity and helped maintaining ionic homeostasis. Conversely, excessive NaHS application under 0 or 150 mM salt stress conditions were found to inhibit protein synthesis, suggesting a complex interaction between stress intensity and H₂S signaling. This study underscores the potential of H₂S as a modulator of plant stress responses, with implications to improve lavender resilience in saline environments.</p>