Maize (Zea mays L.), as one of the strategic crops in arid and semi-arid regions, is highly affected by water resource limitations; therefore, the adoption of sustainable management strategies is essential to maintain its productivity. This study aimed to evaluate the combined effects of biochar, nitrogen, and different levels of deficit irrigation on yield, morphological traits, and water and nitrogen use efficiencies of maize under the conditions of the Sistan Plain. The experiment was conducted as a split-plot arrangement based on a randomized complete block design with three replications. Treatments included irrigation levels (50, 75, and 100% of soil field capacity), nitrogen fertilizer rates (100, 150, and 200 kg ha⁻¹), and biochar application rates (0, 1.25, and 2.5% w/w of soil). At the end of the experiment, stem diameter, plant height, fresh and dry forage yield, fresh and dry ear weight, irrigation water use efficiency, and nitrogen use efficiency were measured. Analysis of variance indicated that the main and interactive effects of irrigation, nitrogen, and biochar on the studied traits were significant at the 1% and 5% probability levels. The highest forage yield, growth traits, and water and nitrogen use efficiencies were obtained under full irrigation combined with 200 kg ha⁻¹ nitrogen and 1.25% biochar application, which did not differ significantly from the treatment receiving 150 kg ha⁻¹ nitrogen. In contrast, severe deficit irrigation combined with low nitrogen input and no biochar application resulted in the lowest values. Overall, the results demonstrated that biochar application at an optimal rate, along with proper nitrogen management, can substantially mitigate the negative effects of deficit irrigation, enhance resource use efficiency, and serve as an effective and sustainable approach to improving maize yield and increasing water and nitrogen use efficiencies, particularly in water-limited regions such as the Sistan area.