The purpose of this study was to measure student affective, behavior, and content (ABC) and global awareness outcomes after participating in a science, technology, engineering, and mathematics (STEM)-based international service-learning (ISL) course and impacts on long-term retention in STEM fields. We compared experiences from 12 participants (undergraduate and graduate students) enrolled in a STEM-based ISL course with experiences from four students enrolled in the same course without the service-learning component. The ISL course involved classroom discussions on environmental topics and four local and ISL projects with community partners to contribute to conservation efforts. Data came from student responses on a civics awareness questionnaire, reflective journal entries, and responses captured during individual semistructured interviews 2 years after the course. Findings indicate positive improvements in affective outcomes, significant gains in civic awareness, differences in behaviors based on class of student, specific content gains related to service-learning activities, global awareness gains for all students, and differential impacts on retention in STEM-related fields.