This article examines the transnationalization of urban policies by analysing the adoption of two ‘foreign’ models of participatory urban planning in the city of Buenos Aires. Both schemes are modelled on internationally acclaimed experiments: Barcelona's Strategic Plan and Porto Alegre's Participatory Budget. In Buenos Aires, however, these policy transfers have failed to produce the remarkable results for which their Spanish and Brazilian exemplars have been internationally praised. Traditional accounts of policy transfers ponder on the institutional compatibility between imported schemes and host environments. The author argues that these works tend to overlook the significance of the stochastic conditions presiding over the adoption of particular policy models in different cities. She proposes to deviate from traditional approaches by seeking an explanation for the poor results of the schemes in Buenos Aires in (a) the contextual conditions framing their adoption in the Argentine capital, and (b) the circumstances surrounding their emergence in Barcelona and Porto Alegre.