Morphological and biochemical effects of different magnesium (Mg) doses on pepper plants under salt stress were investigated in this study. Experiments were conducted under controlled conditions of a climate cabin at 25 degrees C temperature, 70% relative humidity and 16/8 hours light/dark photoperiod. The developmental and metabolic effects of different magnesium doses in plants under salt stress were investigated by examining leaf antioxidant enzyme activities, Malondialdehyde (MDA) levels and chlorophyll contents. Seedlings of 'Demre' pepper cultivar (Capsicum annuum L. cv. 'Demre') were grown in Hoagland nutrient solution supplemented with 100 mM NaCl to generate salt stress. Besides salt treatments, different Mg doses (Mg 1 = 24.64 ppm, Mg 2 = 49.28 ppm, Mg 3 = 73.92 ppm, Mg 4 = 98.56 ppm, Mg 5 = 123.20 ppm) were applied to plants. On the 20th day of salt treatments, the total weight of the plants which is one of the growths and development parameters of pepper plants was measured, and plant samples were taken for analyses. A slight increase was observed in total weights of salt-treated plants with increasing Mg doses. The greatest plant weight was obtained from Mg 4 + salt treatments. It was observed that increasing Mg doses had positive effects on the development of plants under salt stress. Chlorophyll contents and antioxidant enzymes activities increased and MDA (malondialdehyde) levels, the product of lipid peroxidation, which indicates the amount of damage to plant cells, decreased with increasing Mg doses. Present measurements and analyses and resultant findings revealed that Mg treatments at increasing doses partially alleviated negative effects of salt stress on pepper seedlings.