The principle of sincere cooperation can be broadly recognised as one of the basic building blocks of European integration because it allows the creation and maintenance of mutually loyal relations between the Member States and the EU. It guarantees the recognition of general duties of respect, assistance, articulation, and non-contradiction – of coherence of action – between all the public entities covered by the EU legal order, both at the national level of Member States and at the supra-national EU level. This paper will analyse the phenomenon of gold plating in the light of the principle of sincere cooperation. When Member State legislators, while transposing EU law into national law, pass extra norms, guidelines and procedures, in excess of the EU set goals, it is moving away from an effective implementation of EU law. In that way, gold plating can be seen as a breach of sincere cooperation duties allowing a reaction from the EU.