Tourism has an important role to play in the field of sustainability, contributing to the economic development and cultural promotion of territories around the world, particularly European cities. In the context of the growing interest in sustainable tourism, this research aims to analyse the perceptions of the residents of a major European city, Oporto (Portugal), a city rich in history, culture and natural beauty, seeking to develop a more sustainable form of tourism. In methodological terms the research team conducted a questionnaire survey to analyse residents’ perceptions of sustainable tourism practices in the city. 172 responses were obtained, resulting in important data that allowed us to outline the basic profile of residents in the city and understand their perceptions about the concept of sustainable tourism, tourist impacts and their degree of involvement with tourism and potential measures to improve tourist sustainability. The results confirm a widespread optimistic view of tourism development and its impacts on the city, despite some dissatisfaction during the high season. There is also a high awareness of the importance of sustainable tourism, although only a minority is available to actively engage in concrete actions in this field. These conclusions are useful for tourism management entities in the city and reinforce knowledge about the key importance of listening to and involving residents in tourism development processes.