Portfolios have often been promoted as a tool for reflective thinking, yet few studies have examined the use of portfolios in reflective teacher education programs. This exploratory study uses interviews, essays, and survey data to examine 212 teacher education students' efforts to think reflectively through the process of constructing portfolios based on their experiences in a community service-learning program. Findings revealed that the portfolio process prompted reflective thinking in many, but not all, students. Recommendations for using portfolios in teacher education programs include: focusing attention on students' initial understanding of the process and its purpose, encouraging student ownership and individual expression, providing some structured aspects to balance the open-ended nature of portfolios, and evaluating the portfolio process and students' responses.