The impulse buying behavior refers to making an immediate or on-the spot purchases which are without any pre-shopping objective. It is an unintended, non-reflective reaction which occurs after being exposed to some stimuli inside the store. Impulse buying behavior has been classified into four categories namely pure, reminder, suggestive and planned impulse buying. As organized retail is on arise in India, there is a need to understand the impulse buying behavior of consumers in hypermarkets. The research has been reported in two sections. Section I aims to explore shopper's motivations for impulse buying in hypermarkets, to identify product categories mostly purchased on impulse, to determine the post- purchase feelings of impulse buyers and to explore the different types of impulse buying behaviors and their relative frequency of occurrence with respect to the demographics of the respondents. For conducting the research, three hypermarkets were selected from Delhi-NCR. 130 respondents participated in the survey. Content Analysis technique was used for data analysis of the open-ended questionnaires. Based on the findings of section I, data was collected from respondents in a survey in section II to develop a SEM based model of Impulse Buying Behavior in Hypermarkets. The model was tested using AMOS. The results of analysis in section II supports the content analysis technique based findings of section I. The unique contribution of the research in the existing literature is identification of a new category of impulse purchase namely 'Referential impulse buying’. It takes place when shopper's reference group such as friends, family or other shoppers inside the store acts as stimuli for making the impulse purchases. Many new insights have been discussed which shows the influence of demographics like age, gender and occupation on the impulsive buying behavior.