Excessive tourist traffic concentration in cities of high tourist attractiveness often leads to overtourism, manifested, among others, by overcrowding in appealing areas and means of transport, rising prices, or degradation of natural and cultural resources. The effects of an excessive number of tourists include an unfavourable change in the local community's attitude towards tourists. The paper determines the extent and forms of overtourism symptoms in Wrocław, Poland. The research allowed for the identification of negative and positive effects of tourist traffic in Wrocław as perceived by three groups of respondents: experts, Wrocław residents: key experts from the scientific, administrative, planning, and business communities; people directly involved in tourist services; and students of tourism. The crucial part was direct research, conducted in November 2019 with a questionnaire technique. The results confirm symptoms of overtourism in Wrocław, but the threat is not significant. The article shows specific potential overtourism threat factors; the respondents' opinions did not significantly differ between the groups. The presented findings and conclusions may be useful in developing the tourism policy of this and other cities, especially regarding sustainable development of tourism and the potential threat imposed by overtourism. The methodology may be used in similar comparative studies in other cities.