In order to prepare pre-service teachers for their roles in the classroom, it is important to examine the rigor and purpose of the mentoring experience. This study explored the aspects of co-planning conversations that helped experienced and novice teachers expand their expertise and develop a mutually beneficial mentoring relationship at the beginning of a yearlong teacher residency model. While research on co-planning during the student teaching/residency experience exists, this research illuminated the importance of mentoring conversations early on in the teacher residency experience. Using a single case study design, observations, one-on-one interviews, and artifacts from four mentor-mentee dyads, data were examined to gain the essence of a mentoring relationship that utilized co-planning at the beginning of a yearlong teacher residency. Results from this study indicated that co-planning conversations yielded professional development opportunities for both mentors and mentees. Three major themes emerged from data analysis: candid collaboration, dispositional capacities, and ongoing work. These findings further suggest that co-planning can disrupt the norms of the traditional mentor-mentee apprenticeship model. This study can be used to inform teacher preparation programs and school districts about the supports necessary for novice and experienced teachers who participate in yearlong teacher residency programs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]