This study was carried out in a private farm at El-Nobaria region, El-Beheira Governorate, Egypt, during the winter growing seasons of (2015 and 2016) to study the effect of irrigation deficit, (SAB) as  soil conditioner and (protone) as plant antitranspirant on tuber yield and quality of potato crop. The experiments were carried out in a split-split plot design with three replicates. Three irrigation levels (100, 75 and 50 % of reference evapotranspiration) were arranged in main plots, soil conditioner (control, 4 and 8 kg/fed) were arranged in subplots and plant antitranspirant (control, 0.25 and 0.50 L/fed.) were arranged in sub-subplots. The collected data were analyzed using analysis of variance (ANOVA) with the aid of STATISTIX 8 package and significant means separated using Least Significant Difference (LSD) at 5% probability level. The results indicated that the potato yield and its components,significantly increased with increasing water supply up to 100%, application of the soil conditioner at 8 kg/fed., andthe plant antitranspirant at 0.50 L/fed.comparedto other treatments during 2015 and 2016growing seasons. Irrigation at 100% level increased tuber yield by (23.08 and 22.83%) and marketable tuber (3.68 and 3.7%) for both seasons, respectively. Application of soil conditioners increased the tuber yield by (19.21, 19.61%), and marketable tuber by (1.61 and 1.94%), for both seasons, respectively. In addition application of plant antitranspirant increases tuber yieldby 20.87 and19.61% and marketable tuber by about 1.70 and 1.88% for both seasons, respectively. All tuber characters such as (TSS, VC, total carbohydrates, total sugars, protein, N, P, K contents and protein content) increased significantly with irrigation level up to 100%, the soil conditioner(8 kg/fed.), and the antitranspirant (0.5 l/fed.) applications. Based on the present results,it could be recommended that irrigation of potato plants at 100% of ETo with application of soil conditioner (SAB) at 8 kg/fed., and spraying the plants with the antitranspirant (Protone) at rate of 0.5 l/fed. was the most efficient treatments for tuber yield and tuber quality of potato plants grown in loamy soil (El-Nobaria region).