Tour operators are the key elements in the tourism system; they are the link between the tourist and the destination. As a result, tour operators are in many ways the key to achieving more sustainable forms of tourism. This study aims at examining the actual experience of tour operators who adopted sustainability practices in their business with the purposes of: 1) Identifying the priority implementation areas; 2) Determining the most important motivators which encourage tour operators to adopt more responsible strategies; 3) Exploring the outcomes and benefits as well as the major obstacles and barriers that deter the integration of sustainability strategies in the tour operator business. For this study 32 tour operators have been investigated. In addition, in-depth interviews with stakeholders from destinations were conducted to reflect their experience. Results revealed that “Supply Chain Management” has the priority for tour operators during the implementation of sustainable practices. “Building Positive Public Image” is the main reason for implementing sustainability integration in business. The results also outline many benefits for both tour operators and destinations. However, both are encountering a number of barriers that hinder them from applying sustainable principles in the tour operator business on a large scale with more efficiency.