Biomedical engineering (BME) undergraduate students take courses that allow them to develop skills in multiple disciplinary areas (e.g., biology, medicine, chemical, mechanical, electrical engineering) and as such, have a wide array of career opportunities available to them upon graduation. While their broad curricular exposure lends itself to flexibility in careers, it leaves little room in the curriculum for professional competence development and has been implicated in graduates' difficulties navigating career searches upon graduation. This research addresses this concern by examining how students enrolled in an BME program in a highly selective research university fill the professional development curricular gap while pursuing their undergraduate degree. I leveraged professional development educational literature that described concepts of student involvement and experiential learning. These concepts emphasize the importance of active engagement to promote students' learning and development. Through in-depth analysis of the engineering education literature using a systematic search and qualitative synthesis of 100 full articles, I found that assessment efforts in experiential learning settings have largely focused on in-class opportunities and infrequently leverage mixed or qualitative methods of inquiry. This review of the literature informed my year-long qualitative study of BME students' professional development in out-of-class, co-curricular settings. Each of the studies presented in this dissertation analyze data from a series of four interviews with fourteen third-year BME undergraduate students over one academic year. The studies focused on understanding relevant professional development questions for students pursuing BME degrees and engaging in co-curricular opportunities while pursuing their degrees. I found that BME students were most frequently motivated to participate in co-curricular opportunities that they thought had value for their future careers, but also engaged in co-curricular experiences that supported parts of their identities or were generally interesting to them. I also found that BME students described their motivations for pursuing BME in similar ways. Participants in this study discussed personal interests as a motivating factor for pursuing a BME degree, and were able to articulate professionally relevant skills they described as unique to BME graduates. Furthermore, I found data that supports previously anecdotal disciplinary discussions about the career search and exploration process of BME students, finding that across the span of one year, students were discovering multiple new career options, and considering how to address perceived career placement difficulties after completing a BME degree. In my final analysis, I examined the data for evidence of participants' professional competency development over time, looking for patterns in the experiential process by which students developed professional competencies. I found evidence of learning processes connected to the development of ten professional competencies: business, career direction, communication, cultural, design, disciplinary, interdisciplinary, leadership, personal attributes, and teamwork. My work can inform efforts to improve the previously understudied career search experiences of BME undergraduate students. The results of my work indicate the importance of career exploration opportunities throughout students' four-year experience in both curricular and co-curricular settings. My work also has implications for BME educators and advisors interested in co-curricular or experiential learning opportunities. Using the results of my final study as a basis, I have developed a set of recommendations for students interested in selecting co-curricular experiences that support specific professional competence development. Similarly, I recommended curricular strategies educators can incorporate in their classes to support the development of professional competencies linked to experiential, co-curricular engagement in my study. [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.]