Competition law has become increasingly important in regulating the economy. This article aims to explore how domestic competition law relates to sustainable development. It distinguishes three ways that competition law can take into account environmental and social priorities: through substantive competition rules fostering social or ecological purposes; through exceptions, exemptions and exclusions; and through the enhanced application of competition laws. The first form is very interesting and currently not very widely used. Only a very few countries, such as South Africa, have included substantive provisions to promote social development in their competition laws. Most countries allow for some version of the second form of sustainable competition law. Few countries’ laws are as outspoken about their public policy goals as is Spain in its new draft competition law. This new draft law explicitly lists environmental protection and social policies as grounds upon which the government could repeal a competition decision. The third form is relatively unproblematic as it creates a win-win situation for competition and sustainable development. This article surveys some of the most interesting competition law developments across the world and indicates where these domestic regimes take into account environmental or broader social issues when making competition-related decisions such as merger approvals.