This chapter proposes a set of conceptual and methodological foundations for the field of Environmental-Community Psychology (ECP). We propose that this field is structured as an interdisciplinary framework that integrates Environmental Psychology and Community Psychology, whose aim is to analyze and transform the complex relations established between communities and their environments. Through a critical approach, we examine spaces and argue that they are not neutral but disputed venues, where power relations, exclusion, and resistance configure a sense of place and socio-spatial bonds. ECP espouses a situated and collaborative epistemology, highlighting the importance of the knowledge constructed, along with communities, which makes it possible to implement contextually relevant and socially fair interventions. The first section of this chapter addresses key concepts such as sense of place, socio-spatial bonds, space appropriation, and the role of public space in the politicization of community. In its second section, this chapter focuses on the use of participatory methodological techniques such as participatory design, collective mapping, mobile and georeferenced interviews, and photovoice, which foster the active involvement of communities in the management and appropriation of their territories. Through this approach, this chapter helps establish a set of conceptual and methodological foundations for a field of knowledge and action that, in Latin America, has gained relevance due to the complex situation generated by predatory capitalism and an expanding climate crisis.