This study was conducted to quantify crop water stress index (CWSI) based on single leaf temperatures of sunflower and to determine if CWSI values were correlated with other measures of plant water stress. Plant were grown under furrow irrigation and subjected to five water treatments ranging from 100 to 0% (100, 75, 50, 25, 0%) replacement of evapotranspirational losses within 0.90 m soil profile. The yield and water use of fully irrigated sunflower were highest in both years. Trends in CWSI values were consistent with the soil water contents induced by deficit irrigations. An average CWSI of 0.59 before irrigation times produced maximum yield. An equation for calculating yield potential of sunflower was developed using the relationship between yield and seasonal mean CWSI. Moreover, statistically significant correlations were found between CWSI calculated from single leaf temperatures and stomatal resistance, leaf area index (LAI) and available water in the root zone.