This paper addresses the challenges of designing sustainable Information and Communication Technology (ICT) systems. The complexity of ICT systems, the number of stakeholders involved (technology providers, policy makers, users, etc.), and the extension and global scale of ICT supply chain are the main challenges at the core of the complex relationship between ICT systems and the planet Earth. ICT offer an opportunity for an exchange between matter-energy and information: the better use of information offers the great opportunity for decreasing the environmental impact of human activities by decreasing the matter and energy consumption. But, on the other side, like any human activity, the design, production, use, and disposal of complex ICT systems, has as a consequence a growth in entropy. This intriguing dilemma is one of the most difficult challenges in front of designers, ICT companies, users, and policy makers. This paper concentrates on the designers, the engineers’ dilemmas: what are the ethical competences, the skills, the methods for addressing these complex ethical dilemmas? Among the many ethical approaches, the “virtue/future ethics” is proposed as a core ethical competence for the designers and engineers of the future.