Rice–mustard cropping systems dominate large tracts of the Indo-Gangetic Plains, playing a crucial role in food and nutritional security. However, intensive cultivation without adequate nutrient replenishment has led to declining soil fertility and stagnating crop yields. Despite the known beneits of Integrated Nutrient Management (INM), long-term empirical evidence assessing its sustainability in rice–mustard systems is limited, particularly in the alluvial soils of eastern India. Addressing this gap is vital for developing speciic nutrient strategies that enhance productivity while preserving soil health. This study aimed to evaluate the longterm effects of INM on mustard yield, soil fertility, and system sustainability in a rice–mustard cropping system. A ten-year ield experiment was conducted at TCA, Dholi, Bihar. The experiment consisted of ten nutrient management treatments, including control, varying levels of NPK fertilizers, combinations with secondary and micronutrients (S, Zn, B) and the inclusion of organic manure -1 (FYM @ 2.5 t ha ), laid out in a randomized block design with three replications. Results revealed signiicant differences among treatments in terms of growth, yield and economic returns of mustard. The treatment T4 (150% NPK) recorded the higher seed yield -1 -1 (1870 kg ha ), net returns (₹141578ha ) and beneit–cost ratio (1.43), which were statistically at par with T8 (100% NPK + FYM @ 2.5 t ha⁻¹), followed by treatments supplemented with micronutrients. Long-term INM application enhanced soil fertility, with the highest organic carbon (0.50%) recorded under 100% NPK + FYM treatment. Integrated nutrient management proves to be a sustainable strategy for enhancing mustard yield, proitability, and soil health in the intensive rice–mustard system of alluvial soils