Applying transformational critical advocacy research in college instruction can be a powerful way to engage students in challenging inequity in society and promoting positive changes. Few studies systematically measure the impact of such pedagogy on the development of college students' beliefs about advocacy. In this mixed methods study, we worked with 21 preservice teachers through advocacy letter writing activities and collected data from pre/post surveys and focus group discussions to explore the impact of such pedagogy. The findings indicated that advocacy letter writing was a meaningful activity for preservice teachers, allowing them a professional opportunity to voice their concerns about personally meaningful issues to entities in power. A significant correlation was found between baseline advocacy experiences and baseline advocacy beliefs, suggesting that the teaching of advocacy, when combined with opportunities for meaningful practice, can contribute to shifts in belief about the importance of advocating.