Abstract: The present study was carried out during 2004 and 2005 growing seasons on 7 years old Manzanillo olive (Olea europaea, L.) trees grown in Tabouk (36 24` 51.4" E and 28 34` 55.0" N, 765 m ASL), Kingdom of Saudi Arabia (KSA) with drip irrigation system. The aim of the present investigation is to study the effect of irrigation regime and potassium fertigation on vegetative growth, leaf water contents, total chlorophyll, olive fruit and oil yield, fruit quality and nutrients content of Manzanillo olive trees grown under Tabouk conditions. The trees received irrigation water at 25 and 35 m3/tree/year. Potassium fertigation was applied at rates of 0, 200, 300 and 400 mg L-1 K in irrigation water in the form of potassium sulphate (48% K2O). The obtained results revealed that high level of K fertigation (400 mg L-1) improved the vegetative growth parameters, leaf water content and olive fruit and oil yields. Potassium fertigation at high level improved the fruit quality and nutrients contents of leaves and fruits, especially at high level of irrigation water (35 m3/tree/year). Generally, it can be concluded that applying water at 35 m3/tree/year and K fertigation at 400 mg L-1 under drip irrigation system in Tabouk enhanced vegetative growth, fruit and oil yield and improved water and nutrients contents for Manzanillo olive trees.