INTRODUCTION: Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the United States and disproportionately impacts Black individuals. Here, we describe the mixed-methods approach used to develop a tailored message guidebook to promote CRC screening among Black individuals in the setting of recently updated screening guidelines. METHODS: This mixed-methods study included 10 in-depth qualitative interviews and 490 surveys in a nationally representative sample of unscreened Black individuals age ≥ 45. Messages were developed based on American Cancer Society (ACS) and National Colorectal Cancer Roundtable (NCCRT) research findings, tested among Black individuals using MaxDiff analytic methods, and reviewed by a multi-sector expert advisory committee of NCCRT members. RESULTS: The most frequently reported screening barrier in all age groups was self-reported procrastination (40.0% in age 45-49, 42.8% for age 50-54, 34.2% for age ≥ 55). Reasons for procrastination varied by age and included financial concerns, COVID-19 concerns, and fear of the test and bowel preparation. Additional screening barriers included lack of symptoms, provider recommendation, and family history of CRC. Most individuals age 45-49 preferred to receive screening information from a healthcare provider (57.5%); however, only 20% reported that a provider had initiated a screening conversation. CONCLUSIONS: We identified age-specific barriers to CRC screening and tailored messaging to motivate participation among unscreened Black people age ≥ 45. Findings informed the development of the NCCRT and ACS guidebook for organizations and institutions aiming to increase CRC screening participation in Black individuals.