Two field experiments were conducted at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, during the two successive seasons 2012/2013 and 2013/2014. The investigation was aimed to maximize water productivity by intercropping onion on sugar beet through investigate the effect of irrigation and intercropping treatments on onion and sugar beet yield, yield components, quality and some water relations in the North Middle Nile Delta region (31⁰ 07ˉ N Latitude and 30⁰ 57ˉ E longitude with an elevation of about 6 metres above mean sea level). The experimental design was  split plot with three replicates, the main plots were randomly assigned by three irrigation treatments, I₁ (irrigation with 0.8 Ep), I₂ (irrigation with 1.0 Ep) and I₃ (irrigation with 1.2 Ep), while sub main plots were also randomly assigned by intercropping treatments, D₁ (Intercropping onion with sugar beet by planting sugar beet as in pure stand and planting one row only of onion on the back of bed as in pure stand), D₂ (Intercropping onion with sugar beet by planting sugar beet as in pure stand and planting two row only of onion on the back of bed as in pure stand), D₃ (Intercropping onion with sugar beet by planting sugar beet as in pure stand and planting three row only of onion on the back of bed as in pure stand), D₄  (pure stand of sugar beet was planted in bed 120 cm width, spaced 20 cm between hills on both sides of beds to give 35000 plants/ fad.) and D₅ (pure stand of onion with planted in rows on the back of bed, 120 cm width,  15 cm between rows and  hills). The main results can be summarized as follows: The highest values for water applied (Wa) and consumptive use (Cu) were recorded under irrigation treatment I₃ and the values are 69.03 cm. (2899.41 m³/fed.), 73.23 cm. (3075.55 m³/ fed.) for Wa and 41.26 cm. (1733.13 m³/fed.) and 42.25 cm. (1774.55 m³/ fed.) for Cu in the first and second growing seasons, respectively. Meanwhile, the lowest overall mean values for Wa and Cu were recorded under irrigation treatment I₁ and the values are 60.89 cm. (2557.33 m³/fed.) and 34.84 cm (1463.26 m³/fed.) for Wa and Cu, respectively. For intercropping treatments, didn't have any effect on Wa but for Cu, the highest mean values were recorded under D₄. On the other hand, the lowest recorded under D₅. Generally, the values of Cu can be descended in order D₄ > D₃ > D₂ > D₁ > D₅ in the two seasons. The highest values for water productivity (WP) and productivity of irrigation water (PIW) were recorded under I₂ and the values are 23.3 and 22.3 kg/ m³ for WP and 10.3 and 9.3 kg/ m³ for PIW in the first and second growing seasons, respectively. Meanwhile, the lowest mean values were recorded under I₃ and the values are 18.4 and 17.7 kg/ m³ for WP and 8.5 and 8.0 kg/ m³ for PIW in the first and second growing seasons, respectively. For consumptive use efficiency (Ecu), the highest values were recorded under I₃ and the values are 45.98 and 44.69% but the lowest were recorded under I₁ and the values are 42.86% and 40.38% in the first and second seasons, respectively. Regarding, the effect of intercropping treatments generally, the highest values were recorded under D₄ but the lowest under D₅ in the two seasons. Sugar beet yield, yield components and quality were highly significantly affected by irrigation (I), intercropping treatments (D), and the interactions between (I * D) in the two growing seasons. Generally, the highest mean values for the studied parameters were recorded under irrigation treatment under I₂ and intercropping pattern D₄ (pure sugar beet). Onion yield and the studied yield attributes, were highly significantly affected by irrigation (I), intercropping patterns (D) and the interactions between (I * D) in the two seasons. Generally, the mean values for onion yield and yield attributes can be descended in order I₂ > I₃ > I₁ in the two seasons. Concerning, intercropping patterns, the highest mean values were recorded under D₄ (pure onion cultivation) in comparison with other intercropping patterns in the two seasons. Regarding, the interactions between irrigation treatments (I) and intercropping systems (D) & (I * D) showed highly significant effect on all the studied parameters for sugar yield, yield components and quality and also for onion yield and yield components. Concerning, land equivalent ratio (LER), the values can be descended in order I₃ > I₂ > I₁. While, for gross return I₂ > I₃ > I₁. The effect of intercropping treatments, the highest mean values for (LER) and gross return were recorded under D₃ but the lowest under D₁ .