Background: The importance of brand communities is increasing as managers have understood the benefits such communities which can create competitive advantage. Companies are trying to differentiate from the competitors and customer-based brand equity has been acknowledged as a successful marketing tool. Moreover, the development of social media allowed people from different cultures to come together, interact and share experiences in regards of their favorite brand. Purpose: The purpose of this paper is to explain the effect of relationships on social media based brand communities on customer-based brand equity in the service industry. Methodology: The research proposes a sequential explanatory design which consists of a mixed approach by collecting and analyzing the quantitative data first, followed by the collection and analysis of the qualitative data in the form of interviews based on the quantitative results. Data has been collected from Facebook Groups and Facebook Fan Pages in regards of an airline. Findings: Relationship that customers form with the brand, other customers and the service on social media based brand equity have a positive effect on customer-based brand equity. Furthermore, perceived brand trust represents a significant moderator in this relationship. Additionally, results show that there are differences between different cultures in enhancing brand equity. Keywords: Social Media, Brand Communities, Customer-Based Brand Equity, Service Industry, Perceived Brand Trust, Culture