ABSTRACT MARC Supplement at Georgia State University: Workforce Diversity Through Enhanced Mentoring MARC@GSU launched in 2019 and has supported two cohorts of high-performing undergraduates in mentored research and professional development opportunities; a third cohort is being recruited in spring 2021. Despite the pandemic-related challenges, we have successfully matched students with supportive faculty mentors, and they are generating, presenting, and publishing data together. Our mentors are attending mentoring workshops, and our trainees are attending professional development workshops. Nevertheless, sustained mentor-mentee communications and follow-up from workshops are not always optimal. This project proposed in this supplement application aims to develop and test a new tool to foster effective mentor-mentee relationships. We will establish a user-friendly, easily-accessible, online platform through which mentors can create customized mentoring workbooks for use with individual mentees or teams. The platform will support mentors as they guide MARC@GSU scholars toward diverse research career paths. For Aim 1, we will assess current mentor-mentee relationships and identify gaps in mentor preparation, using focus group discussions and literature-based searches. For Aim 2, we will assemble materials and build a platform through which mentors can create customized workbooks with exercises that will help to establish and actively maintain communications and effective mentoring relationships. We will also optimize the platform in collaboration with program directors and mentor-mentee dyads from collaborating institutions, enhancing generalizability of the platform. For Aim 3, we will integrate the new platform into research programs at GSU and make them available for other institutions nationwide, using promotional videos, instructional guides, targeted communiques, and peer-reviewed publications. Strategically designed assessments along with institutionalization and dissemination of the product will maximize the impact of this project. Ultimately, the platform will enhance development of mentors and promote diversity, equity, and inclusion in biomedical research environments.