Barbara Ward was fundamental in promoting an articulated reflection on how to balance economic growth and care for the environment. The article explores how her speeches and writings influenced the standing of policymakers and civil society groups at the Stockholm Conference and after. It discusses how Ward made her mission out of communicating the urgency of the environmental crisis worldwide and how she fought for her idea that promoting the environment had to go together with a fight for social justice and redistribution. From within the Pontifical Commission “Justice and Peace”, she argued that environmental protection was a moral duty and, as such, belonged to the agenda of the Catholic Church. Acting on many fronts, from civil society to the community of experts, to the decision-making elites, through formal and informal networks, she achieved a consensus on establishing sustainable development as a fundamental concern for international politics.