This study investigates how a no-blame culture affects the effectiveness of project-based design teams across different project delivery methods in the construction industry. Ninety-two team members of 34 project-based design teams assessed the no-blame culture, level of teamwork, and team effectiveness in teams that were procured through different routes. A multilevel analysis shows that the relation between integrated project delivery methods, such as design–build and strategic partnering, and team effectiveness varies across levels of no-blame culture. A mediated regression analysis found that the effect of no-blame culture on team effectiveness is mediated by teamwork. Managers of project-based design teams in the construction industry should, therefore, invest both time and effort in creating a no-blame culture and the level of teamwork in parallel. This will enhance the level of team effectiveness in integrated project delivery methods.