Legumes can limit the impact of agricultural systems on the environment by limiting N fertilization, diversifying crop rotation and substituting imported protein-rich feed. However, their production remains low in the European Union, which led to specific policies. France established Voluntary Coupled Support scheme for legumes. Germany did not introduce a coupled support, but provides more favorable implementation of the Nitrates Directive for legumes by allowing spreading manure on these crops. Our study assesses economic and environmental impacts of the coupled support and measures of the Nitrates Directive affecting legume production in France and Germany. We employ the bio-economic model FarmDyn, parameterized for a typical dairy farm in France and Germany. Legumes are introduced as cash crops and on-farm feed, highlighting interactions between crop and animal productions. Different levels of coupled support per hectare were analyzed and the French versus the German implementation of the Nitrates Directive were compared. Results suggest that voluntary coupled support leads to an increase in legume production but to a lesser extend in the German farm than in the French farm, due to higher opportunity costs of legumes. In both farms, the increase in legume production leads to limited environmental benefits: nitrogen leaching and global warming potential slightly decrease. In the French farm, the German implementation of the Nitrates Directive fosters legume production. Thus, this study shows that allowing manure spreading on legumes can help reaching high legume production in livestock farms. However, this further increase in legume production does not lead to environmental benefits. Thus, allowing manure spreading on legumes to increase their production should be justified by other goals such as improving the protein self-sufficiency of the farm.