Hypercholesterolemia is major risk factors for heart disease. Plant sterols have been used for reduction of cholesterol since 1950 decade; so enriching food materials with such components is important. Major problems related to enrichment of products with plant sterols are high melting temperature and chalky taste. In addition, crystal form of these components in comparison with lipid-in solved forms can not significantly reduce the blood cholesterol. In this study enrichment of yogurt and optimization of the process condition were investigated. A four components (plant sterols, emulsifier, vegetable oils and water) mixture design was used to define the percentage of each mixture component to simulate wide range of mixture with different oil quantities. Emulsifier and soy oil were used for dissolving and dispersing of plant sterols in water phase. Yogurt texture, syneresis susceptibility, acidity and viscosity were measures during storage. Gel strength of enriched samples was higher than control. The mean values of syneresis and viscosity of enriched yogurts with phytosterol, were significantly (P < 0.05) lower than the control yogurt. Addition of plant sterol into yogurt did not change titrable acidity. Taste and flavor tested by panelists, where enriched yogurt was preferred to control.