This mixed-methods grounded theory study investigates the development of engineering identity cultivated through engagement in informal learning experiences. In addition, the retention of engineering students and academic performance are investigated for connections to these learning environments. This is the beginning of work to identify best practices for engineering education outside of the formal undergraduate classroom experience. This research provides a framework for investigating the various factors that contribute to the success of low performing engineering students. The essential research categories to the study are (1) Informal Learning Environments, (2) Engineering Identity, (3) Academic Performance, and (4) Retention. The tools used to investigate these categories include peer focus groups and the Academic Pathways of People Learning Engineering Survey (APPLES). APPLES is a research tool developed and used by the National Science Foundation-funded Academic Pathways Study (2010). It is designed to measure engineering students' educational experience, knowledge of the engineering field, and post-graduation plans. The collected data on existing programs and activities -- including summer bridge engineering programs, internships, coops, tutoring, study groups, mentoring, etc. -- suggest that there are connections between the out-of-class commitments of students and their ability to identify with the engineering field. The study also offers performance and retention implications for our low performing engineering students. The research findings unpack salient features for the most noted learning environments and their impact on engineering identity. Through this investigation, the researcher is able to make recommendations for services, programs, and experiences that can support at-risk students completing their engineering degree. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]