Increasing energy efficiency in the building sector is essential if we are to meet the objectives of sustainable development. The district scale offers significant potential for improving energy efficiency, particularly at the early stages of the design. Thus, a transversal approach to the optimization of the energy concept of districts was adopted. It was undertaken using the DIMOSIM (District MOdeller and SIMulator) simulation platform, which provides a detailed analysis of a configuration. The energy, economic and environmental aspects were combined to obtain the best overall performance. The multiobjective optimization procedure is multi-level and includes direct search and the NSGA-ll evolutionary algorithm to deal with the specificities of this particular problem. Indeed, the search space contains continuous and discrete parameters, it is almost infinite and the objective functions are non-linear. This article describes the complete optimization procedure that was developed to solve this complex problem. A case study on the design of an eco-district illustrates the possibilities offered by this type of approach to obtain the best design solutions. (C) 2018 Elsevier B.V. All rights reserved.