The available literature insufficiently discusses the issue of assessing sustainable development of the tourism sector in Poland. Therefore, the aim of the article is to analyse the impact of activities related to sustainable development of the tourism sector in Poland on the opinions of domestic tourists. The convenient sample of respondents consisted of tourists staying in Uniejów during the organisation of the Earth Festival, this in the limitation in the conclusion. The results of the research that employed PQstat programme revealed a significant impact of activities in the sphere of sustainable development of the Polish tourist services sector on shaping the opinions of domestic tourists regarding the implemented activities. The key determinant of sustainable development in this segment—influencing the opinions of consumers of tourism services—is environmental protection activities. Importantly, this aspect is closely related to the economic dimension of activities in the sphere of sustainable development, ultimately influencing the price of offered tourism services. The obtained results enrich source material that can be used by decision-makers in making decisions in shaping the development strategy of the tourism services sector in Poland.