ABSTRACT Background : Irrigation and nitrogen are the main inputs for crop yield and grain quality. Aim : Although studies have been conducted on these applications across different plants, none have focused on yield and grain quality in teff. Methods : This study was conducted to determine the effects of four different nitrogen doses (0, 30, 60, and 90 kg ha −1 ) and three different irrigation levels (50%, 75%, and 100% of ETo value calculated with the use of evaporations from Class‐A pan) on grain yield, yield components, and grain quality traits (protein, starch profile, fatty acid composition) of teff ( Eragrostis tef (Zucc.) Trotter). A key teff cultivar with brown grains was used as the plant material. Experiments were conducted in a split‐plot design with four replications over 2 years. Irrigation, nitrogen, years, and irrigation × nitrogen interactions were found to be significant for all parameters investigated ( p < 0.01). Results : Over 2 years, irrigation water requirements ranged from 340 mm in the I 50 × N 0 treatment to 603 mm in the I 100 × N 90 treatment. The highest irrigation water use efficiency (IWUE; 0.69 kg m −3 ) was observed in the I 50 × N 60 treatment, while the lowest (0.31 kg m −3 ) was observed in the I 100 × N 0 treatment. Similarly, crop water productivity (CWP) ranged from 0.29 kg m −3 (I 100 × N 0 ) to 0.52 kg m −3 (I 75 × N 60 ). For grain yield and components, the greatest grain yield was obtained from I 75 × N 60 treatments (2.52 t ha −1 ), the greatest biological yield was obtained from I 100 × N 90 treatments (6.83 t ha −1 ), the greatest harvest index was obtained from I 50 × N 60 treatments (26.01%), and the greatest thousand grain weight was obtained from I 75 × N 60 treatments (29.39 mg). Increased irrigation levels reduced crude protein content but increased crude ash and phytic acid, causing variations in resistant and total starch. Higher nitrogen doses raised crude protein, crude ash, and resistant starch while reducing phytic acid and amylopectin. The N 90 dose provided the highest resistant starch, and the I 50 × N 90 combination yielded the highest amylose content. Irrigation and nitrogen significantly impacted starch and amylose ratios. Conclusion : For optimal grain yield, biological yield, and quality, the I 75 × N 60 combination is recommended, as it enhances resistant starch, biological yield, and thousand‐grain weight while maintaining balance in plant height and total starch content.