THERE WERE excellent results for tomato yield in hydroponic applications in many countries of the world. It is desirable to look for ways designed to test the ability of two isolates of Pythium oligandrum, isolated from rhizosphere of alfalfa cultivated in Khoaa, Sakaka, Saudi Arabia, to increase yield of tomato in hydroponic system. There were significant increase of fresh and dry matter of shoot, root systems as well fruits of tomato plants cultivated in hydroponic system supplemented with each of P. oligandrum isolates (JU0328 & JU0329). Results showed that hydroponics cultivation system treated with P. oligandrum had beneficial effect on increasing yield of tomato as well as suggesting alternative methods to traditional agriculture, especially in arid areas with poor soil quality.