Critical-thinking skills are a desired higher education outcome and a primary goal in education. This research focuses on fostering college students' critical thinking through reflective writing. During an 18-week study, a total of 60 English majors were recruited. Both quantitative and qualitative data was collected, including 1) the pre- and post-tests of the 5-point Likert scale Reflection Questionnaire, and 2) nine students' reflective essays. The results showed that students significantly improved their critical thinking and revealed four prevalent changes. More specifically, self-worth and volunteerism (two major conceptual changes), as well as patience and gratefulness (two key behavioral changes) stood out among these changes. The implications of using reflective writing to promote students' critical thinking are discussed.