Indeed, the artificial entity ‘Homo-Economicus’ plays a central role in modern neoclassical economic theory. Maybe an illegitimate child of markets’ self-regulation doctrine and the emerging rationalism - professed by the post-modern realms of neoliberalism and the ongoing globalization process - this theoretical abstraction is promoted as a potential prototype of human behavior. It is firmly believed, that this individualistic, self-motivated, and above all, perfectly informed ‘entity’ could, theoretically, lead the economic system into profound balance between supply and demand, consumption and production, utility maximization, and so on. The present paper consists of a criticism to the mainstream prototype of Homo-Economicus, with further extensions to the neoclassical paradigm. Placing this criticism in the context of ecological economics, the paper argues that the notorious rationality of Homo-Economicus seems to be vanished in the deadlock of a futile race towards non-renewable natural resources depletion and increasing environmental externalities. Finally, a brief review of alternative theoretical frameworks and evidence from institutional and behavioral economics, delineates an emerging pressing request for a paradigm change.