Boron is the significant mineral substance for plant development. Although a little amount of boron is sufficient for olive plants, deficient or toxic level of boron causes the negative effect on olive plant development. Boron deficiency should be prevented by applying boron fertilizers. In the case of excessive boron content in the plant tissues, the reasons of excessive boron should be searched. Generally, the most boron toxicity arises from boron contents of irrigation waters. Boron is solution the geothermal hot spring waters easily. Dispersing of the boron contaminated waters to nature without control results in negative effects on plant development. The aim of this research is to determine the toxic level of the boron on olive samplings. Two years old samplings of Gemlik cv. of olive were exposed to irrigation waters contained different boron levels during one year period in greenhouse of Soil Science and Mineral Uptake Department in Adnan Menderes University. 0, 1, 2, 4, 6, 8 ppm boron doses were applied with three replications. Seedlings were planted in 12 kg pots included soil; sand; farm manure in 1;1;1 ratios respectively. Sampling height was measured, leaf and soil samples were collected and samples were analyses for boron. As the result it was observed that leaf boron concentration was increased significantly with increasing boron doses. In the advanced term of sampling development, 4-6 and 8 ppm doses caused the chlorosis in old leaves and burnings on the top sides of plants. The most suitable dose was found 2ppm in irrigation water for Gemlik variety.