Tourism is one of the social phenomena that, under quality leadership and development, significantly improve the country by increasing the GDP, improving transport infrastructure, building appropriate capacities, and communal and other infrastructures. In addition to the many positive aspects that tourism offers, one should not neglect the negative aspects that are more and more pronounced nowadays, not only in the tourism sector but also in other industries of the world, which is primarily environmental pollution. For this reason, trends are increasingly turning towards environmental awareness and more responsible business, keeping in mind the goal of long-term sustainability and a more positive impact on the climate and the environment. When talking about this form of tourism, hotels that have differentiated themselves from the competition with their green business and as a reward boast numerous ecological certificates as proof of effort and investment in new and innovative ideas that are environmentally acceptable. Such hotels certainly attract more attention to the demand, which today is largely educated about green business, so guests expect a higher level of service. Ecological certificates are proof of such practices in the hotel industry, but the problem that arises is the large investment required to achieve strict standards, and owners often give up on such intentions. This paper will explain ecological tourism, its development in Croatia, and analyze ecological certificates based on examples of hotels in Croatia and the world.