The construction industry has positioned itself as one of the main drivers for economic growth and infrastructure development in the world. Nevertheless, this industry remains as one of the most polluting, non-environmentally sustainable, and less committed to the implementation of long-term solutions for sustainable development. Lean construction, as a project management philosophy, has had a positive impact on resource efficiency and productivity of construction projects. However, there are still no several studies that have quantified the environmental impact of this philosophy. The purpose of this research is to quantify the impact of lean construction on the environmental footprint of a project. The methodology of the study consists of a comparative case study, between two projects, one using lean construction principles and the order following a very traditional approach. Both projects were assessed from the environmental perspective through a life cycle analysis using Open LCA. The main results show that there is a quantifiable relationship between the implementation of lean construction and the reduction in the environmental footprint of the project in a range of decrease between 18–24%.