In the digital age of today, the rise of social media has significantly changed how individuals interact, which, in turn, has important implications for the ways in which international business organizations communicate. Although social media was initially created with an intention of bringing individuals closer together, by enabling them to connect with friends, family, and colleagues, it has also become an important everyday reality for most international business organizations and brands, seeking to build, manage and maintain social media brand communities in order to connect with users. Despite the growing influence of social media, immense popularity among social media users, and recognition that businesses should be active and involved, many businesses and brands still do not understand how to communicate neither in brand communities nor with brand community members in social media. While previous research in brand communities has found evidence of strong brand communities and culture based on members’ shared interests and admiration of a brand, limited research has been carried out in relation to the new form of social media brand communities. The aim of this thesis is to present the findings of an exploratory comparative case study of communication in two social media brand communities on Facebook, being the official and global pages of BMW Motorrad and Ducati. The research involved an analysis of brand communication as well as community member communication in one month. The data, which included a total of 123 brand posts, 945 community member comments, and 141 brand responses, were collected using the method of netnography and treated using the method of thematic analysis. The thesis not only answers questions about what and how the respective brands communicate, but also what and how the respective communicate members communicate. The findings show that although both brands communicate by posting content, for example, about their products, and by responding member comments, there is a considerable difference in their brand management perspectives, approaches and efforts. This reveals how BMW uses its brand community as a platform for conversation and co-creation of brand meanings between the brand and its users, whereas Ducati primarily uses its brand community as a transmission channel of marketing-defined brand meanings from the brand to its users. The findings also show that, regardless of the respective brands’ communicative efforts, both BMW’s and Ducati’s brand communities include not only positively-engaged members, who are fans and admirers of the respective brands, but also neutrally-engaged members, who ask or answer questions, as well as negatively-engaged members, who hold hateful and oppositional views of the respective brands. Based on the findings, theoretical and managerial implications, as well as limitations and future research directions, are discussed.