In the study, tomato (Lycopersicon esculentum) variety Adamset F1 seedlings were used. Tomato seeds will be sown in foamed germination pots filled with sieved small-grain pumice and irrigated with tap water. After the excess irrigation water was filtered, the foamed germination pots were placed in a climate chamber with a temperature of 25±2oC and a humidity of 70-80%, covered with papers, regularly checked every day and continued to be watered in a way that maintains the humidity of the pumice. Irrigation was continued with Hoagland nutrient solution in order for the seedlings to develop better in the seedlings. The seedlings, which also formed the second true leaves in the pumice medium, were taken to water culture in plastic tubs filled with Hoagland nutrient solution. Plants were grown in hydroponic conditions in a controlled climate chamber with a light intensity of 400 µmol m-2s-1, a temperature of 20±2 °C and a humidity of 65%, with a dark/light photoperiod of 16/8 hours. 200 ppm, 250 ppm, 300 ppm, 350 ppm and 400 ppm Ca were applied to Hoagland's nutrient solution to determine whether it would increase the drought tolerance of the plants. When the plants had 5-6 leaves, 7% polyethylene glycol (PEG-6000) was added to the Hoagland nutrient solution. Total plant weight, chlorophyll, malondialdehyde (MDA) and enzyme (SOD, APX and CAT) activities of seedlings under drought stress were investigated on the 7th day of stress. In the study, while the total weight of the plants applied PEG+200 and 400 ppm Ca+2 dose was found to be the lowest, it was determined that the plants to which the same dose was applied were damaged morphologically according to the 1-5 scale, chlorophyll was the lowest and MDA was the highest. In terms of SOD and APX amount, the highest application was PEG + 200 and 400 ppm Ca+2. On the other hand, when PEG+250 and 300 ppm Ca+2 doses were applied, total plant weight was high, MDA and enzyme activities and scale values were low.