We applied institutional theory to examine the effect of differences in institutional pressures on strategic decisions of a non-profit non-governmental organization, Greenpeace, in its fight to stop the use of genetically-modified organisms. The effects of differences in institutional pressures were examined through examining differences between the United States and the European Union as well as between two European nations, France and Spain, in Greenpeace’s strategy. We suggested that formal and informal institutional pressures influence strategic decision-making in Greenpeace’s independent national units. We proposed that the US differs from the EU in both formal and informal institutional environments, Spain and France differ in the informal dimension, and these differences are reflected in Greenpeace’s strategies. We also argued that Greenpeace exemplifies the successful use of a transnational strategy and discussed whether non-profits may be better able to adopt a transnational strategy than are for-profits.