Alzheimer's disease (AD)-focused recruitment research registries can help identify eligible participants for AD studies, but registry participation is limited among racial and ethnic groups most at risk for AD. Using the Reasoned Action Approach (RAA), this study is part of a larger project to design theory-based persuasive recruitment messages that would encourage registry enrollment among underrepresented racial and ethnic groups. National survey data were collected in May/June 2021 from adults aged 50-80 years old living in the United States (n = 1,501) with oversamples of non-Hispanic Black (n = 334) and Hispanic (n = 309) adults for group comparisons. Regression analysis was used to estimate the relationship of the attitudes, norms, and perceived behavioral control on intention to sign up for an AD-focused research registry for each racial/ethnic and sex group (i.e., Black women, Black men, Hispanic female, Hispanic men, non-Hispanic White women, and non-Hispanic White men), followed by an audience segmentation analysis based on intender status. Across almost all target groups, attitudes were an important determinant of intention, and norms and capacity were secondary determinants for Black and Hispanic adults, respectively. There was considerable overlap in attitudinal beliefs most salient to the behavior which focused on benefits to society in some way, either generally (i.e., "helping others in the future"; "advancing science") or more specifically (i.e., "helping others like you"). Differences between groups were more apparent regarding norms and capacity. Targeted recruitment messages based on beliefs that were common across the groups could be an efficient way of recruiting people of color into AD research registries.