Soil salinity is one of the major concerns of modern agriculture which poses a threat to food security. This study investigated the mitigating role of Zinc (Zn) on salt (NaCl) stressed foxtail millet, focusing on the modulation of the ascorbate–glutathione (AsA–GSH) pathway. This study evaluated the individual and combinatorial effects of both Zn (1, 2, 3, 4, and 5 mg L−1 Hoagland solution) and NaCl (150 and 200 mM NaCl) treatments on the various morpho-physiological and biochemical parameters of Setaria italica. Salt-treated plants showed a reduction in plant growth parameters, photosynthetic pigments, membrane stability index (MSI), and relative water content (RWC). Contrarily, electrolyte leakage (EL), secondary metabolite content, and antioxidant enzyme activities increased with increased salinity. Lower doses of Zn (1–3 mg L−1) alleviated the negative effects of salinity by boosting the morpho-physiological and biochemical parameters of S. italica. With Zn supplementation, enzymatic antioxidant components, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) showed a maximum increment of 41.86%, 110.88%, 67.38%, 85.74%, 71.44% and 35.84% respectively. Zn treatment successfully improved the redox pools (GSH/GSSG and AsA/DHA ratios) of the salt affected plants. Similarly, non-enzymatic antioxidant molecules, ascorbate (AsA), dehydroascorbate (DHA), glutathione (GSH), oxidised glutathione (GSSG), total phenolics, flavonoids increased by 22.47%, 7.32%, 9.77%, 4.16%, 30.5%, 9.23% respectively. It was observed that higher Zn doses (4 and 5 mg L−1) proved toxic in most of the observations. The enhancement of growth parameters, restoration of the redox status of the AsA, GSH pools and enhancement of SOD, CAT, APX, DHAR, MDHAR, and GR enzyme activities strongly suggests the usefulness of exogenous Zn in enhancing salt tolerance of foxtail millet. This is pertinent in the context of food security as the area affected by salinity is increasing at a rapid pace and thus the mitigants like Zn could be utilized for reclamation.