A two-way factorial experiment based on a randomized complete design (RCD) with four replications was used to compare four levels of N supply including control (N 0 ), 60(N 60 ), 120(N 120 ) and 180(N 180 ) mg N per Kg soil and four different water supply including 100(I 100 ), 80(I 80 ), 60(I 60 ) and 40(I 40 ) % FC on growth, water-use efficiency and mucilage yield of isabgol. Under I 40 , higher N addition led to a significant decrease in root and shoot DM. N addition increased root and shoot biomass especially in I 80 treatment followed by I 60 . The highest (1.71 g plant -1 ) and the lowest (0.42 g plant -1 ) seed yield of isabgol observed in I 100 at N 120 and I 40 at N 120, respectively. The concentration of soluble sugar increased with N supply at I 100 and I 40 . Water stress led to an increase in proline levels, particularly in the N supply treatments. The addition of N tended to reduce the positive effect of water stress on proline content. Seed water use efficiency (WUEg) of isabgol decreased with the increase in drought stress. N supply significantly increased WUEg from N 0 to N 120 with no significant differences between N 60 and N 120 and then significantly decreased by supplying N 180 . Mucillage water use efficiency (WUEm) is also increased linear in all watering regime at all N supply.