Salicylic acid (SA) has an important function in the formation of induced systemic resistance. The aim of this study was to determine effects of exogenous application of 0.5 mM SA on the stress response in duckweed (Lemna minor L.) exposed to the reactive dyestuff Everzol Red LFB (ER LFB). Phytotoxic responses induced by exposure to both ER LFB (75 ppm. 150 ppm and 300 ppm) and 0.5 mM. SA+ ER LFB (75 ppm, 150 ppm and 300 ppm) applications were comparatively examined at 1st. 4th, and 7th days. The lowest chlorophyll a (Chl-a), chlorophyll b (Chl-b), and total chlorophyll (total Chl) contents were found in the 300 ppm ER LFB groups. The carotenoid (Car) content was decreased compared to control groups. The highest total glutathione (GSH), glutathione S-transferase (GST) and peroxidase (POD) activities were found after 0.5 mM SA + 300 ppm ER LFB groups at 7th day. Glutathione reductase (GR) activity was reduced at 7th day. The level of lipid peroxidation, measured as m a londialdehyde (MDA) content was increased generally both ER LFB and SA+ER LFB groups compared to control groups. Results suggest that SA plays a positive role in L. minor against ER LFB.