Twenty-five percent of Americans are first- or second-generation immigrants (US Census, 2012). Thus, it is likely that many Americans identify with at least two cultures, that of the mainstream United States culture, and their ethnic culture from which they came, making them bicultural. However, current understanding of the impact of biculturalism on psychological functioning is quite limited in scope, as few studies have examined this association longitudinally or considered the moderating role of the cultural environment. The present study proposed to take a more comprehensive approach in understanding the consequences of biculturalism on psychological outcomes (i.e., depression, anxiety, and substance abuse symptoms) among Mexican American adolescents, as they belong to one of largest and fastest growing ethnic groups in the United States (US Census, 2013). The present study had two major goals. The first was to examine the influence of biculturalism on depression, anxiety, and substance abuse symptoms longitudinally over the course of two years. It was hypothesized that overall, biculturalism will lead to less depression, anxiety, and substance abuse symptoms. The results partially supported these predictions. For males, biculturalism was related to significantly fewer anxiety symptoms, but not for females. Further, no main effects of biculturalism were found for depression and substance abuse for males or females. The second goal of the study was to examine the potential moderating role of the cultural environment on the influence of biculturalism on mental health symptoms. It was hypothesized that bicultural individuals will exhibit less mental health symptoms in bicultural environments (person-environment fit) compared to more monocultural individuals (person-environment misfit). However, no differences are expected to ii emerge between bicultural and monocultural individuals in monocultural environments, as both groups should be well adapted in these settings. The results did not fully support these predictions. Though, biculturalism for male adolescents was related to significantly fewer anxiety symptoms in home environments where parents reported moderate degrees of biculturalism, and females' biculturalism was related to significantly fewer depression symptoms in neighborhood environments that were relatively bicultural; no effects of biculturalism were found in environments that were the most bicultural. The implications of the findings are discussed.