The topic of this paper is tour operators and mediation in tourism. That is to say, a comparison of tourism and its mediation in the 20th century and the 21st century. The first part, in more detail, illustrates the tourism of the 20th century, its origin, characteristics (among which the widespread stands out) and the essence of mediation. Mediation, as an act itself, facilitated the delivery and sale of tourist products and services, and consequently improved business within tourism. Furthermore, the writing names and addresses the most important tour operators in the second half of the 20th century and proffers an overview of their situation on the market today. Among tour operators, TUI is especially prominent, which has retained the title of the most successful tour operator to this day. The second part of the paper explains the development of tour operators, accompanied by the developments that have occurred in the tourist system as a consequence of the change in the demand of the modern tourist. As each medal has two sides, so tourism among the many positive aspects counts the negative ones. Of the positive ones, specific forms of tourism and pro-poor tourism strategies were singled out. The stated specific forms have been perceived as an important factor in the fight to minimize the negative effects. Likewise, the importance of the fight for sustainable tourism was highlighted amongst the positive aspects. On the other hand, some of the limitations of tourism are: pollution, cruising tourism, shortages of skilled labor and problems of accommodation capacity. Excess of private accommodation and lack of hotels were marked as a problem of accommodation capacities. To present a broader topic of this problem, both types of accommodation are described in particular. Finally, as the fate of tour operators depends on the future of tourism, the expected changes in tourism in the coming periods are defined, and they are referred to the business of tour operators.