The Troubleshooting Portfolios approach was developed at the Olathe Northwest High School in Olathe, Kansas. This approach supports integrated STEM and "informed design" thinking and learning, in which students: (1) use design strategies effectively; (2) work creatively and collaboratively in teams; (3) make knowledge-driven decisions; (4) conduct sustained investigations involving the natural and built world; and (5) reflect on their practices and STEM understandings (Crismond and Adams 2012). Students develop Troubleshooting Portfolios (TPs) to document their evolving prototypes and use evidence from tests they perform to identify problems and suggest improvements. The portfolios support planning conversations that students have with teachers, where evidence leads to creating explanations of what does and does not work with the current prototype and why. This article describes how students can improve design thinking with the use of TPs and provides a sample student Troubleshooting Portfolio.