The overall aim of this two-part study was to develop an intervention targeting sports coaches’ mindsets about their talent as a coach (coach talent mindset, C-TM) and their athletes’ talent (athlete talent mindset, A-TM), called the GrowTMindS Intervention. In this Part I, the intervention was developed drawing on a user-centered design approach and implemented in a coach education program in Norway. The study involved 31 coaches (5 women, 26 men) from 22 to 69 years of age, representing the sports of bandy, golf, ski sports, swimming, and volleyball. Using a mixed-methods approach, the quantitative results showed that the coaches increased their A-TM from pretest to post-test, while their C-TM, which was high at baseline, remained more challenging to target. The qualitative findings helped us understand how most coaches, through reflective processes, perceived the delivery of the intervention as sense-making and substantiated their commitment to growth talent mindsets. The qualitative findings also highlighted areas for refinement and tailoring of the intervention to target all coaches’ talent mindsets. Overall, the study was considered a necessary first step in developing an intervention showing significant and meaningful changes in coaches’ self-reported talent mindsets, consistent with the guidelines of wise psychological intervention and behavior change. © 2024 The Author(s). Published with license by Taylor & Francis Group, LLC.