This article examines how the Child Mathematics Inquiry Portfolio (CMIP), a semester-long field experience project attached to an elementary mathematics methods course, can impact preservice teachers' understanding about teaching and learning mathematics and set them on more positive mathematics teaching journeys as they prepare to enter the field. This action research study, grounded in reflective practice, was contextualized in undergraduate and graduate elementary mathematics methods courses with 92 participants over two academic years. Data came from preservice teachers' written reflections on the child mathematics inquiry process. Findings reveal that the CMIP impacted the preservice teachers' mathematics teaching and learning in four major areas: bridge between mathematics methods course, textbook, and actual classroom experience; mathematical confidence; greater understanding of how teachers shape students' mathematics dispositions; and personal. Implications for mathematics teacher education are discussed.