State enterprises are hybrid actors, situated in between the public and private sphere, and as such their status under international law has long been the subject of contention. More recently, the question of the attributability of their acts to the state has frequently come up in the area of international investment law. If a foreign investor is harmed by a state enterprise, it can only seek redress under international investment law and/or general international law if the acts of the enterprise can be regarded as acts of the home state. The author analyses the criteria capable of addressing the question of attribution of acts by state enterprises. His analysis draws upon a detailed analysis of customary international law and a comprehensive examination of the caselaw of investment arbitration tribunals, the World Trade Organisation, the European Court of Human Rights and the European Court of Justice. The author also discusses the role of lex specialis treaty rules on attribution.