This article provides a general overview of the technical, economical, regulatory and environmental aspects of ecolabeling. An ecolabel is a market-based policy instrument that can be either voluntarily adopted or mandated by law. Ecolabels are applied to services and products in order to inform consumers of their environmental-friendliness and to avoid market failures. In reality, however, ecolabels do not always succeed in achieving environmental improvements. The mis-use of environmental standards, the practice of strategic manipulations that create trade-distortions, the excessive use of claims, and behavioural biases are some of the factors that can prevent an ecolabel from reaching its initial objective to reduce or even eliminate environmental externalities.