After the liberalisation of the electricity and natural gas markets, the importance of the generation and protection of competition within these markets has increased. In order to introduce competition into the markets and to protect the existence of competition, both regulatory rules and competition law has started to be implemented by regulatory and competition authorities. In particular, with the consideration of the decisions of the EU Competition Commission and the European Court of Justice, it could be underlined that competition investigations and decisions are used to establish or to protect a competitive environment that has not effectively been built in those markets. In this study, the electricity and natural gas markets within the scope of the EU have been examined, and the strategy adopted during competition investigations is discussed with a critical perspective.