In order to ensure long-term quality tourism, sustainability of natural resources and avoid permanent damage to the environment and preserve biodiversity, it is important to responsibly use or manage protected areas, including the Lonjsko Polje Nature Park. The aim of this paper is to determine sustainable forms of tourist offers of the Lonjsko Polje Nature Park in order to preserve the biological diversity of the area and to examine the attitudes of Zagreb residents about the impact of certain types of tourism on biodiversity conservation in the park. A survey was conducted on a sample of 160 adult respondents living/residing in the City of Zagreb. The obtained data show that most of the respondents did not visit PP Lonjsko polje, but those who did, mostly visit it once a year, spend a day there and mostly visit agritourism. The main reason why other respondents did not visit the Park is insufficient information, and most of them said that they want to visit Lonjsko polje and a good promotion would encourage them the most. Most of the respondents stated that they do not know how much tourism is developed in the area of the Park, but they believe that this area is suitable for performing tourist activities. They also believe that informing visitors/users about responsible behavior in nature would have the greatest impact on biodiversity conservation and that gastronomic and sports-recreational forms of tourism always have an impact, while educational tourism does not affect biodiversity at all. All respondents generally agree that caring for the environment has a positive effect on the conservation of biological diversity in the area and that the Lonjsko Polje Nature Park has the potential for the development of eco-tourism.