This article examines the Mathematics, Engineering, Science Achievement (MESA) program and investigates its impact on underrepresented student populations. MESA was started in California during the 1970s to provide pathways to science, technology, engineering, and mathematics careers for underrepresented students and represents an exemplar model of informal learning environments. Using a mixed-method research design of investigation, this exploratory study looks at the relationship between MESA activities and underrepresented students' self-efficacy, interests, and perceptions related to engineering. Evidences for this study includes data from focus-group interviews conducted and results from quantitative data collected using the Engineering, Self-Efficacy, Interests, and Perceptions Survey (ESIPS) instrument. Results from this study suggest that participation in MESA's activities has a positive influence on underrepresented students' self-efficacy, interests, and perceptions related to engineering.