Extensive studies have been conducted over the decades to evaluate the possibility of using diluted seawater for irrigation of plants. This study determine the effects of seawater irrigation on vegetative growth changes of Manilkara hexandra seedling as the rootstock of sapodilla. A pot experiment was conducted in a greenhouse using different concentrations of seawater (3, 6, 9, 12 ds/m) on the one-old age seedling and fresh water used as control. Increasing seawater concentration, decreased the diameter of stem. However, compared with control, no significant differences were found in different characters of root and stem. Leaf area increased significantly firstly (6ds/m) however significantly decrease with increasing concentration of seawater.