A field experiment was conducted during Rabi 2021 at Crop Research Farm, Department of Agronomy, SHUATS, Prayagraj (U.P), India. This study aims to determine the effect of phosphorus and boron levels on growth and yield of mustard (Brassica juncea L.). The soil of experimental plot was sandy loam in texture, nearly neutral in soil reaction (pH 7.2). The experiment was laid out in a Randomized Block Design consisting of nine treatments with three replications. The treatments comprising of different levels of phosphorus and boron whose effect was observed in mustard. The results obtained that the application of Phosphorus @ 60 kg/ha along with Boron @ 2.0 kg/ha was recorded significantly higher Plant height (187.59 cm), Plant dry weight (37.92 g/plant), Number of Siliquae/plant (319.80), Number of Seeds/siliquae (14.60), Test weight (5.19 g), Seed yield (2.61 t/ha) and Stover yield (4.55 t/ha). Therefore, treatment with the application of Phosphorus @ 60 kg/ha along with Boron @ 2.0 kg/ha was more productive and cost effective.