This study acknowledges the potential contribution of Mexican highly-skilled immigrants settled in the United States. Then, to better understand how the brain waste phenomenon (unemployment/underemployment) functions among these immigrants in the United States, by using the lens of neo-racism, Latina/o Critical Race Theory (LatCrit), and Bourdieu's Reconnaissance of Capitals, this qualitative study analyzed tertiary-educated Mexican immigrants (MeXpatriates)´ lived-experiences in securing and maintaining employment in the United States, as well as the meaning that these actors make of these experiences. Through Hermeneutic (Interpretive) Phenomenological Analysis (IPA), the study captures the lived-experiences of 21 MeXpatriates residing in the Arizona, U.S. -- Sonora, Mexico border region, collected via in-depth, open-ended interviews and analyzed using Atlas-Ti software. The study finds that tertiary-educated MeXpatriates do not necessarily arrive in the United States with a meticulously outlined migration plan or the intention of permanently settling in this country. Also, it consistently reveals the existence of a broad range of migration stories and the recurrent reliance of these MeXpatriates on family legal migratory status to complete its legal migration process to the United States. Additionally, it highlights the presence of intense emotional bonds with their partners and relatives and the belief in a positive future after relocating from Mexico to the United States. Another significant finding is that within the U.S. labour market, tertiary-educated MeXpatriates are not subject to involuntary unemployment as these individuals become employed upon actively seeking jobs. However, as part of their migratory pathway in this land, these MeXpatriates frequently experience underemployment (brain waste phenomenon). Interviewed MeXpatriates also informed on life situations and major conditionals that they perceive as contributing to their experiences with underemployment: individual-based life situations and environmental-based life situations. Individual-based situations contributing to tertiary-educated MeXpatriates' underemployment experiences in the U.S. labour market are the status of facing in-process migratory paperwork, lack of a U.S. work permit, responsibilities on child-care, the personal need to have an entry-level job, a feeling of fear grounded on the decision of not to participate in the workforce for a long term, monetary necessity, the personal decision to stay in the field of expertise, and the lack of appropriate local credentials. On the other hand, environmental-based life situations include an existing model of human resources exploitation & profits, a business mindset supporting having high-quality laborers with low pay, a must-have experience in the migration from Mexico to the United States, and racism. Within the life situations shared by this study participants, three major conditionals emerged in fostering the underemployment of tertiary-educated MeXpatriates: a restricted English language proficiency, unfamiliarity with the U.S. labour market & tertiary education, and an underdeveloped social capital. Additionally, four underemployment scenarios are identified within tertiary-educated MeXpatriates' experiences: high physical labor (housekeeping, food preparation), office labor (front-desk receptionist, call center representatives), experienced labor (entry-level international business jobs), and professional labor (with demand of high expertise/formal education but in job positions below their level of formal education).This study also revealed the rationalization of underemployment as part of the adjustment to a new country and a necessary component of the migration Mexico -- United States. Although underemployed, these participants perceived their U.S. earnings as superior to potential earnings in Mexico, leading to gratitude for employment and its associated benefits. Despite all the aforementioned challenges, some tertiary-educated MeXpatriates in this study demonstrated an active approach to pursuit better employment opportunities, including enhancing English language proficiency through employment and ESL classes, valuing Spanish as an employability asset, pursuing further education in U.S. institutions, securing community support, participating in internships, and leveraging their social networks via educational programs focused on highly-skilled migration. This study advanced the current understanding of the U.S. brain waste phenomenon among highly-skilled immigrants by providing a comprehensive first-hand portrayal of tertiary-educated MeXpatriates' employability experiences as expressed by these contemporary phenomenon's living actors. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. 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