Two field trials were carried out at South Tahrir Research Station (Ali Moubarak), during 2005/2006 and 2006/2007 to evaluate irrigation water requirements and determine an irrigation schedule for cassava crop under different plant interspacing. The study included two irrigation interval (daily and every two days interval), two quantities of applied irrigation water (100%of the ETc and 80%of the ETc) and three-plant interspacing (75cm apart, 100cm apart and 125cm apart). A split split plot design was used. The results indicated that yield components of cassava, i.e., was increased the total number of tubers per plant, the average length and diameter of tubers  and the weight of fresh tubers/ plant  when used two days interval irrigation  associated with 100% Etc and  increasing plant spacing up to the widest one (125cm apart.). Whereas, maximum yield of cassava tubers and water applied were associated with irrigation each two days interval and 100% ETc under the narrowest spacing of cassava plants (75cm. apart.). Whereas, maximum value of water use efficiency (WUE) was obtained every two days interval irrigation with 100% ETc and plant spacing up to the widest (125cm. apart).