Abstract Non-technical summary There is abundant research about the impacts that large-scale mining produces on territories to the detriment of their social and environmental sustainability. However, during our research in Chile and Peru, we also identified local transformative initiatives that pursue sustainable development by proposing alternatives to how the socio-ecological impacts of natural resource extraction are produced and distributed throughout society. Specifically, we ask the question: How do local communities in Chile and Peru that are affected by mining activities engage in community-based environmental monitoring (CBEM)? Technical summary By examining how local communities in Chile and Peru engage in community environmental monitoring, this paper argues that local political organisation and institutional innovations are crucial for the emergence of transformations towards sustainability. Local political organisation and mobilisation can create a window of opportunity for discussion about extractive activities and their impacts, as well as possible proposals for alternatives. Institutional innovations triggered by local political work can lead to the implementation of such initiatives. Our findings are based on qualitative case studies of CBEM in Chile and Peru, in areas with high levels of environmental degradation due to mining. In Chile we analysed a case of community air monitoring in a copper processing area, and in Peru a case of community water monitoring in a mining area. Drawing on debates on social transformation and political ecology theory, this study aims to show CBEM promotes changes towards a more democratic and preventive environmental governance, and encourages the recognition of environmental injustices. Social media summary This paper analyses how local communities in Chile and Peru engage in community environmental monitoring in areas affected by the presence of extractive industries. We identified local transformative initiatives that pursue sustainable development by proposing alternatives to how the socio-environmental impacts of natural resource extraction are produced and distributed in society. Our findings are based on qualitative case studies of community-based air and water monitoring in extractive areas in Chile and Peru.