Accurate and complete environmental information is at the basis of any effective sustainable development policy. This report summarises for the first time the status of air, climate, water and soil in the Western Balkans (WB), describing current knowledge as of 2021 and gaps with respect to the EU aquis in order to: a) benchmark the progress during the accession process, and b) support the implementation of the Green Agenda for the WB with particular reference to depollution and decarbonisation priorities. This information is also relevant for the EU Green Deal zero pollution ambition, as depollution in WB also reduces pollutant levels in neighbouring EU Member States. Despite significant improvements in the alignment of the climate and GHG emissions monitoring and reporting legislation and the good progress in the areas of air and water pollution in the latest two years, the EU aquis implementation is still lagging. The overall WB air quality situation is still critical and the pollution trend is often upwards, despite PM10 and PM2.5 concentration have decreased in certain areas. Due to its dominant impact on mortality, PM2.5 can be considered the main pollutant to target in the WB. The energy sector, in particular coal-fuelled power plants, is the major source of SO2 and CO2 emissions and an important source of other pollutants. It offers a concrete opportunity for co-benefits between air quality and climate policies. The increase in intensity and frequency of summer heatwaves in the latest decades is an indicator of climate change in the WB and the need to design appropriate adaptation plans to cope with it. The status of waterbodies in the WB can generally be assessed as unsatisfactory. In the case of chemical status, 45% of waterbodies assessed failed to reach good status, while in the ecological assessment 54% failed to reach good status. Case studies on antibiotic resistance, as well as effect-based studies on mixtures of pollutants confirmed that aquatic ecosystems, particularly large fluvial rivers, are under considerable anthropogenic pressure. Soil degradation is prevalent and extensive throughout the WB region. Soil erosion is the most relevant degradation process followed by soil pollution. Unsustainable land management practices and natural causes of soil degradation in the region are interlinked. In order to make progress in the implementation of the environmental legislation it is necessary to improve the integration of the environmental measures into key sectorial policies (e.g. energy production, energy efficiency, industry, transport). This principle is reflected in the Green Agenda for the WB and the new EU Soil Strategy. Due to the relatively small area of the WB and the interconnections between ecosystems across and beyond the region, strengthening regional and international cooperation is essential to involve all the relevant actors and stakeholders in the design and implementation of environmental policies.