Background: Maize is an important food security crop cultivated in Ethiopia. However, the productivity of the crop is markedly low due to low soil fertility and associated with low soil nutrient availability especially nitrogen and phosphorous deficiencies and the use of inappropriate fertilizer management practices. Objective: A study was conducted in Haramaya District to investigate the effects of mineral nitrogen fertilizer application rates on yield components and yields of maize varieties during the 2019 and 2020 main cropping seasons. Materials and Methods: The treatments consisted of two improved maize varieties (BHQPY 545 and MHQ 138), one composite open-pollinated variety (Raare-1), and six rates of nitrogen fertilizer (0, 23, 46, 69, 92, and 115 kg N ha-1). The experiments were laid out as a randomized complete block design in a factorial arrangement and replicated three times per treatment. Data were collected on thousand kernel weight, stover yield, grain yield, and agronomic nitrogen efficiency. The data were subjected to analysis of variance. Results: The main effect of nitrogen application significantly (p ≤ 0.05) affected thousand kernel weight and harvest index. The highest thousand kernel weight (346.6 g) and harvest index (44.8%) were obtained in response to the application of 92 kg N ha-1. The interaction effect of maize variety and nitrogen rate significantly (p ≤ 0.05) influenced stover yield, grain yield, and agronomic nitrogen efficiency. The highest stover yield (9.62 t ha-1) and grain yield (9.13 t ha-1) were recorded for variety BHQPY 545 at 92 kg N ha-1, which resulted in 55.6% and 67% more grain yield than MHQ 138 and Raare-1 varieties, respectively. The MHQ 138 and Raare-1 varieties produced only 5.9 t ha-1 and 5.5 t ha-1 grain yield at 92 kg N ha-1, respectively. The highest net benefit (138222 Ethiopian Birr ha-1) at 115 kg N ha-1 and marginal rate of return of 301% were obtained from variety BHQPY 545 at 69 kg N ha-1. Conclusion: It is concluded that the BHQPY 545 variety produced the optimal grain and stover yields, with the highest net benefit and marginal rate of return at 69 kg ha-1 as well as with the highest agronomic nitrogen efficiency that exceeded the agronomic nitrogen efficiency of MHQ 138 and Raare-1 by about 2.4-fold and three-fold, respectively. This implies that cultivating this variety at a relatively moderate rate of nitrogen fertilizers enhances the yield of the crop for improving food security and farmers' livelihood in the study area. [ABSTRACT FROM AUTHOR]