Objective: To investigate what key stakeholders consider to be the advantages and the opportunities for improvement in using lean thinking and tools in the integrated project delivery (IPD) process. Method: A detailed literature review was followed by case study of a Lean-IPD project. Interviews with members of the project leadership team, focus groups with the integrated team as well as the design team, and an online survey of all stakeholders were conducted. Analysis: Statistical analysis and thematic content analysis were used to analyze the data, followed by a plus-delta analysis. Results: (1) Learning is a large, implicit benefit of Lean-IPD that is not currently captured by any success metric; (2) the cardboard mock-up was the most successful lean strategy; (3) although a collaborative project, the level of influence of different stakeholder groups was perceived to be different by different stakeholders; (4) overall, Lean-IPD was rated as better than traditional design-bid-build methods; and (5) opportunities for improvement reported were increase in accurate cost estimating, more efficient use of time, perception of imbalance of control/influence, and need for facilitation (which represents different points of view). Conclusion: While lean tools and an IPD method are preferred to traditional design-bid-build methods, the perception of different stakeholders varies and more work needs to be done to allow a truly shared decision-making model. Learning was identified as one of the biggest advantages.