The Socio-Environmental Fund CASA is a mechanism to mobilize resources, support and build capacities of grassroots environmental groups. Its mission is to promote environmental conservation and sustainability, democracy and social justice by supporting and strengthening the capacities and initiatives of civil society in South America. A non-profit, non-governmental organization in Brazil, the Socio-Environmental Fund CASA mobilizes and channels financial and capacity-building support for the social and environmental initiatives of NGOs and community organizations. Thus, the Fund seeks to create conditions for persons and groups to strengthen their work and achieve better results with their actions, always aiming at socio-environmental sustainability in the South American territory. CASA has supported groups that monitor actions and decisions in the South American territory, put in practice innovative solutions for socio-environmental challenges, as well as communities affected by megaprojects. At every step, the need for CASA to become a major social investor in South America becomes more evident.