Heat Exchanger Network (HEN) synthesis approaches based on total annual costs (TAC) optimization can reduce CO2 emissions and electricity used in plants, since the use of utilities is reduced with a cost optimal design. However, environmental impacts (El) are not explicitly addressed in such methods. Life cycle assessment (LCA) metrics can quantify El and can be used as objective function. This work proposes a meta-heuristic approach to perform a multi-objective optimization (MOO) of TAC and EI in medium and large-scale HEN. The method developed efficiently achieves near-Pareto fronts for four industrial-size case studies. Optimal-TAC and optimal-EI solutions, as well as configurations with low El but still competitive TAC are presented. Cost-optimal solutions reported in the literature are compared with non-dominated solutions obtained in this work with similar TAC. In all cases, the approach developed is able to achieve solutions with remarkably lower El, demonstrating the importance of multi criteria optimization in HEN synthesis. (C) 2017 Elsevier Ltd. All rights reserved.