Water is the most important factor limiting crop productivity at different growth stages of crop growth and development. The study was conducted to investigate the effect of irrigation scheduling on sunflower hybrid (Hysun-38) at vegetative versus reproductive stages during spring season 2010. The trial was laid out in randomized complete block design (factorial arrangement), replicated thrice, having net plot size of 3.5 m × 9 m. The treatments comprised of irrigation application of 75 mm each, at different growth and development stages. viz., I₁ = irrigation at plant establishment, I₂ = irrigation at plant establishment and irrigation at vegetative phase, I₃ = irrigation at plant establishment, irrigation at button stage and irrigation at flowering, and I₄ = irrigation at plant establishment, irrigation at vegetative phase, irrigation at button stage and irrigation at achene’s formation. Days taken to 50% flowering was highest in I₂, where irrigation was applied at plant establishment and vegetative phase, and in I₄ treatment , where irrigation was given at seedling establishment, irrigation at vegetative phase, irrigation at button stage and irrigation at achene’s formation. Leaf area index at different growth intervals was significantly affected by irrigation levels. Crop growth rate was highest for treatment I₄. Plant height (PH), stem girth (SG) head diameter (HD), 1000-achene’s weight (AW) and achene’s yield (AY) were significantly affected by different irrigation levels at various growth stages. Maximum AY (2415.68 kg·ha^-1) was obtained in I₄ treatment while, minimum AY (1275.35 kg·ha^-1) was obtained in case of those plots which were irrigated only at plant establishment stage. Sunflower productivity was affected with irrigation regime at different growth stages with the strongest responses seen at early growth stages which ultimately affected the final achene yield adversely.