This study apply coconut water to support the process of formation of potato tubers in vitro. The study was conducted at the laboratory of tissue culture, Experimental Garden of Vegetable Research Center, Berastagi, North Sumatera. The experiment used Completely Randomized Design with single treatment factor, the coconut water concentration of 0; 75; 150 and 225 ml L−1. The results show that the application of coconut water provides a significant effect on the number, diameter and fresh weight of potato micro tubers, but the effect is not significant at the time of potato micro tuber formation. The application concentration of coconut water 225 mL L−1 affected the potato micro tuber formation in in vitro.