More and more clear consequences that arise in the environment due to irrational use of natural resources have made sustainable development today important. In tourism, sustainable development is also imposed as a priority and necessity, but in practice it often encounters obstacles to its implementation. The problems that arise in applying the principles of sustainable development in tourism can be a result of the conflicting interests of the key stakeholders. To avoid this, there is a need to establish an adequate system of communication between all stakeholders. An important group of stakeholders in the sustainable development of tourism are tourists who, due to their stay in a tourist destination, can achieve positive and negative environmental impacts. In order to suppress their negative environmental implications, there should be a way to influence the creation or the increase of their ecological awareness. The heterogeneity of tourist demand, i.e. different wishes, habits, attitudes, opinions, needs and beliefs of tourists makes this task difficult. Creating ethical codes and establishing codes of conduct for tourists while staying in a tourist destination can significantly contribute to sustainable development, however, it is necessary to find an adequate medium through which the message on the importance and necessity of environmental protection will be transferred in the right way and at the right time to tourists. The aim of the paper is to show the role that social networks can have in creating the ecological awareness of tourists. By developing modern technologies, social networks have become the medium through which a person most often communicates with the others, where one records information about him/herself and where one can get information about others. In tourism social networks play an important role in creating marketing strategies, because they represent an instrument that allows the destination to interact with tourists and to find out and observe their opinions, attitudes and evaluations of services in tourism. Through social networks, tourists find inspiration for new travel, share tips and experiences with other users, share travel photos, and they can be informed about the tourist destination offer. Researches show that there is an increasing number of social network users and that they spend a significant part of the day using them. By analyzing the role that social networks have in tourism marketing, it can be concluded that they are a medium by which messages that can influence the increase of the tourists` ecological awareness can be created and by which the messages about the codes of ethics and rules of tourists behavior can be transmitted even before the tourists travel to the destination. The specificity of social networks can make this message more durable and created in a way that is consistent with the heterogeneous characteristics of the tourism market. Nevertheless, in using social networks for creating tourists` ecological awareness, there should be a careful approach and there is a need for additional research on how tourists or potential tourists use social networks.