Historically, profitability and efficiency objectives have been the prevailing interest for organisations. However, the move towards green operations has forced companies to seek alternatives to combine these with green objectives and initiatives. Green lean is the result of this combination. The purpose of this paper is to critically discuss the green lean approach and the potential benefits of integrating Six Sigma to enhance its effectiveness. The paper is based on a literature review that discusses the synergies and differences of lean and green, and its main limitations. Departing from the limitations identified, the paper then proposes Six Sigma, and specially its problem solving methodology DMAIC, as an approach that may help in overcoming the limitations of green lean. Thus, the paper conceptually proposes Green Lean Six Sigma. It intends to offer academics, researchers and practitioners interested in lean and green with some initial conceptual ideas regarding their possible integration with Six Sigma.