Polyhalite popularly known as POLY4 is a multi-nutrient fertiliser containing K, S, Mg, Ca, and micronutrients. POLY4 has a low carbon footprint, is certified for organic agriculture, and has the potential to improve crop productivity and quality attributes Indian mustard which often faces challenges due to imbalanced nutrition supplied in the current fertilisation schedule. The hypothesis of the study was that the multi-nutrient fartiliser POLY4 can ensure balanced nutrition for Indian mustard. Considering this, a field experiment was conducted during the winter seasons of 2017-18 and 2018-19 to evaluate the effect of POLY4 on Indian mustard (Brassica juncea L.) with respect to its yield, quality, and nutrient uptake. POLY4 along with conventional sources of nitrogen (N) and phosphorus (P) was compared to recommended fertilisation practices from conventional sources of N, P, K namely urea, di-ammonium phosphate (DAP), and muriate of potash (KCl). With the application of POLY4, seed yield was significantly improved by about 600 kg ha^-1 compared to NP control (no application of K and S) across the two seasons. Compared to recommended practice of NPK, the yield was increased by about 450 kg ha^-1 with the application of POLY4. Mustard seed oil and protein percent were also improved with the use of POLY4. POLY4 did not have any adverse effect on the content of anti-nutritional factors and improved the omega-3 fatty acid content of mustard oil. Higher uptakes of macro and micronutrients in the crop were also recorded with POLY4 along with an improved soil nutrient status. From the economic point of view, it was also observed that the application of POLY4 resulted in an increment of net returns of USD 45-60 comparing cultivating mustard with the conventional N, P, K, and S fertilizers only. Therefore, the use of POLY4 as a source of multi-nutrient for balanced nutrition helped to increase the efficiency of applied nutrients which ultimately improved the yield and quality of mustard. This study exhibits the pioneer findings of polyhalite (POLY4) based balanced nutrition in Indian mustard.