Tourism growth in recent years increased visitor density in several urban destinations, a situation that appeared more strongly in border cities due to their geographical location, natural attractions, commercial capacities, and continuous travel flows that exposed them to higher tourism pressures than many other areas. Under these conditions, overtourism, as a result of visitor numbers exceeding destination capacity, could generate economic, social, spatial, and environmental challenges and influence various urban functions. The present study aimed to examine tourism growth in border cities and explain the effects of overtourism dimensions as factors contributing to urban sustainability challenges in the city of Marivan. This research was applied in purpose and conducted through a quantitative approach. The statistical population consisted of residents of Marivan, and the sample was selected using random sampling. Data were collected through a researcher made questionnaire based on the theoretical foundations of overtourism, covering economic, cultural, infrastructural, environmental, managerial, and political dimensions, and its validity and reliability were confirmed. Data analysis was performed using structural equation modeling. The results showed that the dimensions of overtourism played a role in creating tourism pressures and the emergence of urban unsustainability, and some dimensions had a greater influence in explaining this situation. Overall, overtourism appeared as a multidimensional phenomenon that disrupted the balance between tourism development and urban sustainability, indicating the need for managing visitor capacity, strengthening infrastructure, and adopting coordinated policies to reduce its negative effects.