<p>Professional engineers think and act in distinctive ways when addressing engineering problems. Students need to develop this reasoning or engineering thinking during their education. Unfolding the undergraduate students’ thinking is a necessary step in designing experiences and teaching materials that foster not only their understanding of engineering concepts but also their learning to think as professional engineers. While there are previous studies about the students' thinking in other disciplines, more research is needed in engineering. This three-study dissertation aims to further our comprehension of undergraduate students’ engineering thinking using an adapted version of the Engineering Habits of Mind (EHoM) model. Specifically, the dissertation’s studies work together to continue the research that addresses the question:<em> What are the characteristics of undergraduate students</em>’ <em>engineering thinking?</em></p> <p><br></p> <p>The first study used naturalistic inquiry to holistically explore the cognition associated with the EHoM of senior chemical engineering students when improving a chemical plant. The analysis of students’ interactions showed that their redesign process followed an iterative co-evolution of the problem and solution spaces. Furthermore, they treated the task as a socio-technical problem considering engineering and non-engineering factors. In addition, while exploring problem and solution entities, they used multiple representations to communicate ideas but had difficulties translating symbolic representations into more physical, concrete representations. Regardless the technical issues and time constraints, the students completed the conceptual redesign and communicated their proposal to the client.</p> <p><br></p> <p>The second study used qualitative content analysis to examine first-year engineering students’ ideation as a cognitive skill associated with the EHoM of problem finding and creative problem solving. Particularly, it focused on students’ ideation of questions and recommendations when doing data analytics to help improve a client’s enterprise. The analysis of students’ reports showed that they expanded the problem space of the task by bringing additional information that was not provided. They asked questions focused on performing statistical analysis of the dataset and requesting information about the company’s business model. At the end of their data analytics, students made high- and low-quality recommendations considering their alignment with a specific problem, robust evidence, and the client’s needs. </p> <p><br></p> <p>The third study used qualitative descriptive research to investigate undergraduate participants' cognitive competencies within engineering systems thinking at the International Genetically Engineered Machine (iGEM) competition. These competencies are associated with the EHoM of problem finding, creative problem solving, systems thinking, and visualization. Mainly, the study focused on analyzing the evidence of cognitive competencies documented in the publicly available participants’ wikis where they registered their design process. Results showed that iGEM teams developed solutions with biological systems interacting with other systems and used concepts and tools from multiple disciplines. They also cooperated with stakeholders, which helped them analyze their system from multiple lenses. Moreover, depending on their upfront task, they fluidly represented their systems from structural, behavioral, and functional perspectives. </p> <p><br></p> <p>The final chapter of this dissertation presents an overarching discussion across the studies. The findings and implications will support curriculum designers, instructors, and other interested readers to prepare learning environments that promote undergraduate students’ engineering thinking. Furthermore, they may guide future efforts to continue exploring the students' thinking process when addressing engineering problems. </p>