There is an ever-increasing need for technologically literate citizens to find creative ways to solve societal problems. STEM, the integration of science, technology, engineering, and mathematics subjects continues to be a popular topic as schools grapple with how to best prepare students for an ever-evolving society. As societal and technological challenges emerge, design thinking has been lauded as a method to enable people to help tackle those challenges. The steps of the design thinking process, "empathize, define, ideate, prototype and test" align with engineering design and can be used as a problem-solving method in classrooms to help promote creativity, critical thinking, and collaboration. The purpose of this explanatory sequential mixed methods study was to better understand if a STEM integrated curriculum helps promote design thinking in middle schoolers. The study compared two middle school groups, one that uses an integrated STEM curriculum and one that does not. Quantitative data was collected through the design thinking disposition survey through pre and post testing. Qualitative data was collected through free response questions and student and teacher interviews. There was no difference found in the change of design thinking dispositions between students at the two schools, however students scored lowest on the design thinking disposition of "prototype." Free response questions showed that seventh grade students at the STEM integrated school perceived an increased ability to design solutions to problems. Student and teacher interviews highlighted benefits of using a STEM integrated curriculum including providing collaborative opportunities to solve hands-on, open-ended problems. How STEM curriculum can develop design thinking should continue to be examined including how to scaffold student understanding of design processes like clearly defining the problem and building prototypes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]