This research assesses the lean and green (LG) practices' impact on the competitive advantage (CA) of organizations, through sustainable performance, considering lean maturity as the moderator. A structured questionnaire was used to collect data from a cross‐sectional sample of 261 companies operating in Portugal. Hypotheses are tested through structural equation modeling and multigroup analysis to examine the lean maturity moderating role. Results demonstrate a positive impact of LG practices on sustainable development and that their three dimensions of CA, with lean maturity boosting most relationships. This research highlights the impact of LG practices on organization's competitiveness and helps them underpin the importance these practices when comes to enhance their sustainable performance and their CA with help of environmental policy and also stakeholder engagement. Future studies should address these relationships upon a specific dimension, namely the correlation between environmental performance and CA, as it was not dealt in this study.