Protected areas (PAs) are considered one of the most important ecotourism destinations in terms of biodiversity and having abundant capabilities and attractions. Since ecotourism activities do not always lead to economic benefits and environmental development, it is necessary to investigate the negative impacts of ecotourism activities in these areas. For this purpose, in this study, the Delphi method and SWOT-ANP model were used to investigate the negative impacts of ecotourism activities on the four types of PAs of Tehran province and provide optimal strategies. According to the results, the highest mean negative impacts of ecotourism in Lar National Park include unplanned development of ecotourism activities, reduction of dense pastures due to bush cutting, trampling, and lack of adequate monitoring, and in the Jajrud protected area, the trend of land use/cover changes, due to the development of ecotourism infrastructures and the increase in the demand of urban communities for the development of recreational activities. In the Tangeh Vashi National Natural Monument, the most negative impacts include the increase in environmental pollution due to the high number of ecotourists compared to the area's size and facilities, and finally, in the Kavde Wildlife Refuge, the highest mean is allocated to the increase in illegal hunting of wildlife due to the lack of monitoring mechanisms. In the following, to control these impacts, optimal strategies were selected by examining the strengths, weaknesses, opportunities, and threats based on the expert's viewpoint, which include offensive-competitive strategy (SO) in Lar Park, defensive strategy (WT) in Jajrud area and the diversification strategy (ST) due to TangehVashi, and Kavdeh refuge, which should be considered by managers in planning and decision-making.