An experiment was conducted to determine the effect of paclobutrazol (PBZ) and different irrigation amount on growth of aerial parts, leaf minerals and root performance in young olive plants cv. ‘Manzanillo’ in the Department of Horticulture, Faculty of Agriculture, Tarbiat Modarres University in 2000. A split plot experiment in time was used based on a completely randomized block design with four replications. The aim of this experiment was to determine the effect of water irrigation amount reduction on Manzanilo olive response. Treatments were 60, 70, 80, 90 and 100 % evapotranspiration (ETp) and 60% with 0.25 g a.i /pot paclobutrazol (PBZ). Control plants were used as reference to determine evapotranspiration (ETp). Some characteristics such as root, leaf and shoot fresh and dry weight, leaf area, leaf number, plant height, root length and mineral content were measured. Results indicate that root, leaf and shoot fresh and dry weight, leaf area, leaf number, plant height and N and K amount were increased with increasing of water amounts. No differences were found in measured characters between 90 and 100% (ETp) so a 10 percent saving in water was occurred. Result showed that pbz treatment after 45 days reduced shoot growth, leaf and shoot fresh and dry weight, leaf area, plant height, root length and N and K content. Although, PBZ treatment increased root to shoot fresh and dry weight ratio and increased root diameter. In case of water shortage pbz treatment is able to ameliorate the effect of water stress.