Efficient use of nitrogen and water is vital for sustaining crop production in arid regions. A field experiment was conducted to assess the effects of arbuscular mycorrhizal fungi (AMF) inoculation (inoculated vs. non-inoculated), three irrigation water regimes (IWR; 50%, 75%, and 100% of crop requirement), and five nitrogen rates (0, 46, 92, 138, and 184 kg/ha) on tef (Eragrostis tef). AMF, IWR, and N significantly influenced grain nitrogen, zinc, iron, and selenium uptake, grain protein content (GPC), agronomic use efficiency (AUE), physiological use efficiency (PUE), apparent recovery efficiency (ARE), and water use efficiency (WUE), while site and season were not significant (P > 0.05). Under 100% IWR with AMF inoculation, and 184 kg/ha N recorded increases of 793% in grain N, 468% in Zn, 502% in Fe, 488% in Se, 131% in GPC, and 583% in WUE compared to the lowest input treatment. Importantly, AMF inoculation with 92 kg/ha N optimized AUE (37.2 kg/kg) and PUE (83.3 kg/kg), representing increases of 233% and 93% relative to non-inoculated controls. Integrating AMF with 92 kg/ha N inputs enhances nutrient acquisition, protein content, and water productivity, providing a sustainable pathway to improve crop performance in resource-limited arid environments.