This qualitative study developed a preparation series to prepare principals in the approach of Cognitively Guided Instruction (CGI) to support teachers in implementation. The series included six virtual sessions that prepared principals in understanding the “Why” behind CGI, the connection to the state standards, number sense routines, the unpacking/solving/share-out of story problems, and the analysis of student work. The series also included two site walkthroughs where the principals observed number sense routines and the unpacking/solving of story problems. During the walkthroughs, the principals were able to debrief together and identify strong feedback to provide teachers. Data collection methods included reflection exit tickets after each session, observations, document analysis after the walkthroughs, and one-on-one interviews with each participant at the conclusion of the study. Results from the study suggest that the preparation series was successful in preparing principals to support teachers implementing CGI. The findings revealed all participants had a perceived change in understanding around students’ thinking and were able to identify key principled ideas of CGI. The study concluded principals need to work with their colleagues to be strong instructional leaders who learn with their teachers, place a focus on math, and understand how to support their staff with implementing the approach of CGI. Future research should focus on preparing principals and teachers together in the approach of CGI and creating a cohort-based model for support in implementation and sustainability.