Mustard is an oilseed crop with a high protein which has emulsifying, stabilizing, antioxidant, flavoring, properties. The purpose of this project was to investigate the effect of different concentrations of yellow mustard on the stability, viscosity, rancidity and organoleptic properties of mayonnaise .For this purpose, different amounts of yellow mustard powder (0, 0.1, 0.2, 0.3, 0.4, and 0.5%) were used in mayonnaise formulation. The result of physicochemical experiments showed increased viscosity, improved emulsion stability and decreased rancidity of mayonnaise by increasing the percent of yellow mustard and undesirable changes happened to mayonnaise color and taste. The result indicated that the mayonnaise containing 0.5% yellow mustard powder was suitable due to high viscosity, good emulsion stability, low range of rancidity but with respect to organoleptic experiments, the mayonnaise containing 0.3% of yellow mustard powder was the best mayonnaise (p< 0.05).Still, further works are yet required to increase the functional properties of yellow mustard and to decrease the undesirable changes happening to mayonnaise color and taste.