In response to the post-pandemic shifts in the construction industry, many projects in Canada have implemented collaborative delivery methods and management strategies, such as integrated project delivery (IPD). These relational delivery methods are based on applying various Lean construction practices during the project lifecycle to improve collaboration and sustainability. However, due to extreme fragmentation in the construction industry, achieving sustainable collaboration between project participants in IPD projects is challenging. In addition, the interplay between Lean practices and sustainability in IPD projects is yet to be discussed. Therefore, applying suitable Lean construction practices in various phases of IPD projects is needed to address the existing challenges, improve collaboration, and enhance sustainability. The goal of this research is to identify appropriate Lean construction practices in various phases of IPD projects and propose a framework for selecting these phase-based LC to maximize collaboration in IPD projects. This study follows a multi-step research methodology, namely, a literature review and focus group discussions with practitioners in the construction industry of Quebec, Canada. The results illustrate the maturity of applying lean practices in the design and construction phases of IPD projects. This research contributes to a deepening knowledge of lean practices that can drive collaboration in IPD projects.