This paper assesses the political viability of free trade agreements (FTAs) in the presence of lobbying by organized foreign interest groups. The assessment is based on a model in which external tariffs and the decision to form an FTA are endogenously determined. The findings demonstrate that, in the presence of an organized lobby group in a prospective partner country, an FTA may initiate an increase in the level of protection against imports from third countries and impede trade with non‐member countries. Further, this study finds that a foreign lobby may encourage the local government to enter a welfare‐reducing trade‐diverting FTA. Finally, this paper shows that an FTA increases the lobbying power of the organized lobby groups of the member countries, which can potentially obstruct the viability of welfare‐improving multilateral trade liberalization.