Background: This study was conducted to determine the effects of boron levels on germination and seedling growth of melon cultivars under laboratory conditions. Methodology: The seeds of three melon cultivars (Hasanbey, Kırkağaç, and Toros Sarıbal) were germinated at different boron levels (0, 20, 40, 60, 80, and 100 mg L-1) constituted by sodium borate (Na2B8O13.4H2O). Germination percentage, mean germination time, germination index, seedling growth parameters, and seedling dry matter were investigated. The optimum and toxicity levels of boron were calculated by regression analysis. Results: Germination percentage, mean germination time, and germination index were not affected by increasing boron levels. A boron dose of 20 mg L-1 promoted root length, shoot length, and seedling fresh weight of melon; however, seedling growth of melon cultivars was inhibited at higher boron levels than 40 mg L-1. Seedling dry weight and dry matter significantly enhanced when the boron levels were increased. Root length was more sensitive to boron than shoot length. Melon cultivars showed different responses to boron levels and the highest seedling growth parameters were obtained from Kırkağaç. The optimum boron level for shoot growth was calculated as 12.8 mg L-1, while the inhibitory level of boron for root growth was 65.4 mg L-1. Conclusion: The toxicity of boron on the germination performance was not detected and higher levels than 20 mg L-1 inhibited seedling growth of melon.