This System Dynamics model describes interactions between different sectors of the socio-ecosystem of the Mar Menor coastal lagoon and the surrounding Campo de Cartagena watershed in south-eastern Spain. The model allows simulation of the current situation and of the impacts of a ‘Business Roadmap’ consisting of 14 solutions under different scenarios of socioeconomic and climate change. Model output is presented as impacts on multiple Key Performance Indicators of sustainability including environmental, social and economic aspects. Through these simulations, the model aims to support integrated planning and better informed decision making. The model, developed in Vensim software, allows making integrated assessments regarding interactions between agricultural development, water and nutrient balance, sustainable farming practices, rural and coastal ecotourism, renewable photovoltaic energy facilities, social awareness and governance, economic profit and jobs, and the ecological status of the Mar Menor lagoon. The simulation provides information regarding impacts on a broad range of Key Performance Indicators (e.g. ‘nutrients in Mar Menor’, ‘pressure on water resources’, ‘irrigated land area’, ‘Mar Menor degradation status’ ‘coastal-rural recreation potential’ ‘number of expected tourists’, ‘photovoltaic energy potential installed’, ‘total gross economic benefit’, ‘number of jobs’, etc.). The structure of the System Dynamics model was co-developed through an extensive participatory modelling process. In this process, consisting of workshops, expert interviews and questionnaires between 2018 and 2022, stakeholders from all sectors identified the main interactions between sectors as well as potential solutions that could help reach a jointly developed future Vision for the area. Mental maps of the interactions between sectors that were developed during this participatory process formed the starting point for the System Dynamics model and can be consulted in Martínez-López et al. (2022a). The ‘Business roadmap’ and its 14 solutions that were also co-developed through this participatory process, are described in detail in Martínez López et al (2022b). The time series of input data for the Business roadmap and for the socioeconomic and climate change scenarios are reported in Martínez López et al (2022c) Martínez López & de Vente (2022) respectively, but are also an integral part of the model itself. The model can be run in Vensim PLE (Personal Learning Edition) that is free for educational use, and it includes a dashboard that allows to easily evaluate the impacts of different combinations solutions under different scenarios.