ABSTRACT This study involved exploring the opportunities of using regulated deficit irrigation and partial root zone drying approaches as water-saving irrigation methods in a tomato crop (Solanum lycopersicum L.) based on irrigation scheduling. The Partial Root Zone Drying Irrigation practice simply involved interchanging the wet and dry sides in subsequent irrigations. The field experiment was conducted in the Kingdom of Saudi Arabia, during the fall season of 2014-2015 and 2015-2016. The following three irrigation treatments were tested during both years under a drip irrigation system: (1) full irrigation (FI), as a control treatment; (2) regulated deficit irrigation (RDI); and (3) partial root zone drying irrigation (PRD). Both RDI and PRD treatments received 70% of the irrigation water volume of full irrigation (FI). The obtained results indicated that the soil water content of PRD treatment was higher and conserved more soil moisture than that in the RDI treatment. Data for both years indicated that FI exhibited the highest stomatal conductance (gs) values while PRD exhibited the lowest gs values among all the treatments. Under PRD treatment, the dry fruit yield was the highest when compared with RDI and FI treatments for both years. Deficit irrigation treatments result in higher abscisic acid (ABA) concentration in the xylem when compared to that in FI. The vast majority of most extreme irrigation water use efficiency (IWUE) values were involved with PRD while most of the minimum IWUE values were coupled with FI. These results indicate the effects of deficit level irrigation on IWUE