This study aims to compare two Swedish Environmental Non-Governmental Organizations (ENGO:s) in relationship to their international establishment, for the purpose to gain a more nuanced knowledge of how they operate to achieve their goals, and a better understanding of the challenges and benefits the different international establishments can bring. We interviewed two ENGO:s, Naturskyddsföreningen and Jordens Vänner, on the basis of two main issues:- How can work to influence environmental policy differ between a Swedish ENGO and an international ENGO operating in Sweden?- What are the challenges and benefits of influencing Swedish environmental policy for ENGO:s in Sweden that are different internationally established?This study used the method of Most Similar System Design to answer the main issues in the selection of cases, and further a semi-structured interview was used to collect empirical data. The main theory to analyse the data drew from Beyers (2004) conceptualisation of mobilization strategies in from of access and voice.The empirical study shows that the difference in international establishments indeed brings both challenges and advantages to the ENGO:s operationalization. The Swedish established Naturskyddsföreningen could engage in a more local matter, were they influenced both members to be more active and local politicians and political decision-makers. But the inefficient way to combine both access and voice proved to be a challenge in articulating certain core issues. The international established Jordens Vänner showed a different way of conducting environmental policy, by using their international networks as a way of influencing the policy process. But restrains from their internationally management proved limit the space and possibility to operate.Keywords: NGO, ENGO, environmental governance, policy process, mobilization strategies, institutional actors, local engagement, networks