This chapter aims to contribute to the debate on European parliamentary (EP) oversight by examining how institutional access to official secrets as well as leaks unauthorised disclosure of official secrets affect the oversight role of the EP in foreign policy. It provides an analysis of how through leaks and informal channels of communication, the EP is able to conduct oversight in foreign policy. The reliance of parliaments on executive actors to access information is inherent in the structure of their relation since it is the executive that has the main prerogatives in foreign policy and hence holds the information. The chapter focuses on how access to classified information and leaks affect parliamentary oversight. It shows that leaks can play a significant role for a more informed EP and facilitate oversight, future research should further enquire to what extent leaks politicise parliamentary oversight in foreign policy and possibly undermine trust between parliaments and executive actors in the matters of international relations.