Some medicinal plants need to be cultivated commercially in order to meet the ever-increasing demand for medicinal plants for the indigenous systems of medicine as well as for the pharmaceutical industry; in this regard, it seems significant to test the important medicinal plants for their salt-tolerance capacity, with a view to exploiting the saline lands for medicinal plant cultivation. Phyllanthus amarus plants were grown in the presence of NaCl in order to study the effect of NaCl (80 mM NaCl) in the induction of oxidative stress in terms of lipid peroxidation (TBARS content), H2O2 content, osmolyte concentration, proline(PRO)-metabolizing enzymes, and antioxidant enzyme activities. Groundwater was used for irrigation of control plants. Plants were uprooted randomly on 90 days after sowing (DAS). NaCl-stressed plants showed increased TBARS, H2O2, glycine betaine (GB), and PRO contents, whereas NaCl uptake decreased proline oxidase (PROX) activity and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased under salinity.