Terminal drought is the main factor limiting the yield of cereals in the central area of Spain because rainfall is scarce and temperatures are high during the grain-filling period. The response of 12 cultivated barley (Hordeum vulgare L.) genotypes consisting of 6 breeding lines showing high yield under terminal water stress and 6 commercial varieties was studied in a rain shelter. Trials were performed over 3 years to determine the influence of terminal water stress on yield and yield components and the relationship between yield and phenological and agronomic traits. When the crop reached the flag-leaf stage, half of the experimental plots were subjected to a water-stress treatment and the remainder were maintained at optimal water conditions. Variations were observed in number of days to ear emergence, days to maturity, and length of grain-filling period. Precocity strongly influenced the length of the grain-filling period so that the earlier genotypes had the longest grain-filling periods. Among yield components, mean grain weight had the greatest influence on yield under terminal water stress conditions. Earliness and length of grain-filling period were the phenological traits that most influenced yield in water stress conditions. These traits and harvest index (HI) showed a significant correlation (P < 0.001) with grain yield. Earliness, mean grain weight, and HI contributed to greater yields under terminal water stress.