The Accreditation Board for Engineering and Technology (ABET) which accredits higher education programs globally, has placed the ability for students to recognize professional and ethical responsibilities among their seven stated student outcomes that undergraduate engineering programs must ensure their students achieve to maintain their accreditation. This is to ensure that these students are appropriately prepared to enter professional practice (ABET, 2021). Because of this, along with the importance of engineers understanding their obligations to act ethically in ensuring public safety and professional integrity, there is a need to better understand the ethical decision-making of undergraduate engineering students. Knowing what factors may increase or decrease their tendency to act in accordance with their ethical obligations could shed light on different curricular and co-curricular approaches undergraduate engineering programs should consider in determining how to effectively train their students in the subject of professional ethics. Two factors of particular importance in ethical decision-making are a person's disposition toward self-interest--something that can have potentially devastating consequences in engineering--(assessed here by their agreement to a Machiavellian worldview) and their behavioral tendency to make certain decisions within professional practice in light of that disposition. Of particular interest to this study were students' tendencies to make either cooperative or non-cooperative choices in a forced-choice scenario as well as abide by their professional obligation to hold public safety paramount. To answer this question of possible associations between undergraduate engineering students' ethical behavior, their ethical dispositions, and other possible mitigating factors (e.g. gender, co-curricular activity, and professional preparation), a survey was conducted which collected 110 responses from undergraduate students at a R-1 institution located in the American Northeast with both engineering and business/management programs. 85 of the respondents were undergraduate engineering students and 23 were business/management majors. Only two of 110 participants scored in the High-Mach region of the Mach-IV instrument, signaling an agreement with a Machiavellian disposition. Significant relationships were found between student participation in affiliation-based co-curricular/professional preparation experiences (e.g. professional society membership, student organization membership, etc.) and lower Mach-IV scores. Additionally, engineering students and women were also more likely to take part in affiliation-based experiences than business/management students. A qualitative analysis of student explanations of their ethical decisions found that students differed in their definitions of what constituted engineering work, with some students understanding it more broadly. The strong influence of a student's understanding of real-world professional practice/organizational culture on their ethical decision-making was also apparent. Finally, students were found to not always consider public safety as a non-negotiable value if the safety risk was deemed 'minor'. Also, due to the low presence of High-Mach individuals in the sample population, the study raises the question of whether the Mach-IV instrument, as currently devised, is a suitable measure of ethical disposition for the current generation of undergraduate students. [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.]