In today's modern world, more and more importance is given to sports and a healthy lifestyle. Sport provides undoubted physical and mental advantages and promotes mutual connection, because sport as such does not know any social, cultural and geographical boundaries, but enables entertainment and encourages the strengthening of togetherness by opening doors to new worlds. The media play a big role in the popularization of sports, and presence of social networks has led to a revolution in all industries, including sports. Social networks, as an element of mass communication, are an integral part of everyday communication in sports, because sport would certainly not be what it is without the media, which have a positive, but sometimes negative influence. The most important functions of communication via social networks are internal and external communication, branding of sports, i.e. sports clubs and athletes, and promotion. Most sports clubs, especially football clubs, are active through all possible social networks where they have their official profiles through which they can communicate with fans about all the news related to the club itself and the players. Public relations and communication through social networks are an absolute imperative in the daily business and operation of football clubs. The main gols is through public relations and social networks to better connect with all shareholders, especially the target group - the fans, and give them importance by showing a sense of gratitude and respect for the trust, loyalty and support the fans provide them. Sport needs the media for greater reach and better promotion, but sport also needs the media for the abundance of attractive content and information that attracts a large audience. In the second part of this thesis, through the casy study, a comparison of communication on social networks between FC Barcelona and GNK Dinamo Zagreb will be presented.