Social media are widespread and easily accessible communication tools and as such have become a means of Internet activism, or the place of mobilization and education of citizens for non-profit organizations and associations. In the doctoral dissertation, we explore the social media communication strategies of animal welfare organizations in the context of Internet activism. The main aim of the research is to analyze the communication values and the role of social media in the work of the associations for the promotion of the animal rights and welfare, with special reference to the new values in the fight for the animal rights and welfare and the benefits for the users who communicate with the associations via social media. Specific goals are; to determine which social media is primly used by organizations to promote animal rights and welfare, to identify the main intent or purpose of the messages posted by the associations on social media, more precisely on Facebook in the context of Internet activism, and to show the benefits that Facebook of the associations has for the users. The scientific contribution is the analysis of the communication strategies of non-profit organizations and new knowledge on the ways and possibilities of social media use for the associations. The theory of networked society is the first starting point of the dissertation. For Manuel Castells (2004), a networked society is a social structure composed of a number of networks based on information and communication technology. For Jan Van Dijk (2013), a networked society is a form of a society that organizes its relationships in media networks by gradually replacing or supplementing face-to-face communication. The agenda setting theory is the second starting point of the dissertation since the associations for the promotion of animal rights and welfare use the media (Facebook) to set the agenda to its audience or users. The theoretical framework for research related to users benefits from Facebook is found in the theory of uses and gratifications. The Internet is a place to meet a number of needs; communication, information, entertainment, creation, participation, support and so on. The dissertation is created in the field of information and communication sciences, so the emphasis is on the research of the media, media content and media effects. The dissertation consists of two parts. The first part deals with relevant literature in the field of information and communication sciences, psychology, sociology, philosophy and cultural anthropology that exams topics such as; animal welfare, animal welfare on the Internet, networked society, Internet, social media, Internet activism and so on. The second part is an empirical research. The research is carried out by using quantitative methods („Internet data mining‟, quantitative content analysis and Internet survey) and qualitative method (semistructured interview). In the first part of the research, by collecting Internet data, we present which social media the associations for the promotion of the animal rights and welfare use in their work. In the next part, by using content analysis, we present what kind of messages prevail on Facebook pages of these associations. Also, what kind of user activity and user comments prevail on their Facebook pages. In the third part of the research, by using semistructured interview, we present why do the association choose Facebook as a means of communication and what are their opinions on benefits and disadvantages of Facebook in their work. Finally, by using an online survey, we present the opinions of the users on the benefits that they have from Facebook pages of these associations. We have confirmed three hypotheses; animal rights and welfare associations use Facebook as the primary means of communication and information, the majority of Facebook messages of the animal rights and welfare associations are trying to encourage the public to foster animals, and the benefits for the users of Facebook of associations is the exchange of information, advice and education.