Nowadays, the subject of Brand is one of the critical subjects that companies and marketers are focused on it and the accomplished conferences and published articles about this subject in recent years is the reason of focusing marketers on this critical subject. In the subject of marketing, the subject of Brand Loyalty, is one of the important and even vital issues in the marketing of the present world and especially adult markets on which numerous investigations on that have been accomplished in modern countries and numerous articles have been written that companies, by using the guidelines and notes offered in these studies, benefit the privileges of loyalty establishment in their own customers. In this study, it has been tried to extract important and common items by extended studying in the field of affecting factors on Brand Loyalty, and giving exams on them so that we can extract the main factors of loyalty establishment (in this case, in the market of dairy products of Tehran) so that we can use them as guidelines in the steps of active companies. The reason for choosing markets of dairy products was that in present, this market concerning to the existence of multitudinous companies in which customer loyalty has a deep role in their remaining. The steps done are as follows: At first, the definition of Brand Loyalty is explained. After pointing out the generalities of the discussion, the concepts of the investigation were pointed out that these concepts on the strength of studies were accomplished which were ended in the loyalty of customers of dairy products. Then six hypotheses are extracted from these concepts and we tested the extracted hypotheses by questionnaire tool. As the final outcome, the effective factors in brand loyalty of dairy products in Tehran city market sequenced as follows: Price, Taste, Advertising, Packaging, Availability and word of mouth. In the end, the summarizing, concluding and suggesting were accomplished.