This study was carried out in a greenhouse in the pot experiments in order to determine the effects of the irrigation water salinity on leaf carbon isotope ratio of maize (Zea mays saccharata). Salinity treatments were imposed by irrigation water containing NaCl, CaCO3, MgSO4 salts and having electrical conductivity of 0, 1.5, 3, 5 and 10 dS/m. The experiment was conducted in a completely randomized plot design with 3 replications. The fully expanded leaves were collected for carbon isotope analysis. Then plant samples were harvested for dry matter analysis. Carbon isotope ratio of leaves and crop yields were strongly affected by increasing irrigation water salinity. According to the results of the research, leaf carbon isotope ratio (Delta L; C-13 %) has increased in parallel with the increase of the irrigation water salinity. While the average carbon isotope ratio of leaves in T1 is at the lowest (4.00), the average carbon isotope ratio of leaves in T5 is found as the highest (4.65). Crop yields decreased with increasing irrigation water salinity. The highest yield (33.14 g) and the lowest yield (8.22 g) was found. A negative correlation was observed between crop yields and carbon isotope ratio of leaves.