The purpose of this study was to analyze the effect of differentiation, product quality, brand equity, and product knowledge on purchasing decisions for Yakult drinks in Purwokerto. The sample of this research is part of the community in Purwokerto, which comes from four sub-districts namely East Purwokerto, West Purwokerto, North Purwokerto, and South Purwokerto totaling 105 respondents using purposive sampling technique with several criteria that have been required and data obtained from respondents with research instruments using a questionnaire. The data method used in this research is multiple regression analysis. The results showed that differentiation, product quality, brand equity, and product knowledge had a simultaneous effect on purchasing decisions. The results reveal that brand equity has a significant effect on purchasing decisions, product quality has no effect on purchasing decisions, brand equity has a significant effect on purchasing decisions, and product knowledge has no effect on purchasing decisions.