Our purpose was to provide a model for a middle school design thinking program supported by a university-school partnership and to investigate potential benefits of teaching middle school students to be design thinkers. Sixth, seventh, and eighth grade girls (N = 80) participated in the Innovation Nation program. Over three days, students engaged in workshops and collaborated in teams to learn the five phases of design thinking (empathize, define, ideate, prototype, and test) and applied the methodology to an authentic human-centered innovation challenge. Student teams showcased prototypes of their solutions at a final exhibition attended by parents and the school community. Results showed that participants dramatically increased their understanding of design thinking and its steps as a result of the Innovation Nation experience. Notably, there were also important gains beyond design thinking knowledge, including increases in self-efficacy for creativity, design, and problem-solving, and better attitudes about group work. There was also evidence that skills learned in Innovation Nation transferred, as students showed an increased tendency to seek critical feedback and revise work based on feedback in a novel design task following the program. We hope to encourage middle school educators to bring design thinking into the curriculum, as students who learn design thinking also develop important habits of mind and 21st century skills.