Abstract The Alzheimer’s Disease (AD) Sequencing Project Phenotype Harmonization Consortium (ADSP-PHC, U24- AG074855) includes data from 30+ AD research cohorts and represents the largest ongoing effort in the United States to collect metadata from cohorts for genetic research in Alzheimer’s disease and related dementias (ADRD). The Veterans Health Administration’s (VHA’s) Million Veterans Program (MVP) is one of the world’s largest genetic research databases, with more than 950,000 United States Veteran participants, including ~650,000 with available whole-genome genotype data and a subset of those genotyped participants (150,000) with whole-genome sequencing data available soon. MVP participants also reflect the diverse demographics of Veterans who receive care in VHA—in fact, the MVP includes one of the largest Black and Hispanic genetic cohorts in the US, who are currently underrepresented in large-scale genetic investigations. However, to date, due to strict privacy policies, MVP-participant data has been inaccessible to non-VA investigators. To promote greater use of MVP data, VHA has initiated development of VA Data Commons, a platform that will enable the analyses of MVP data by researchers outside the VA. This competitive supplement to the ADSP-PHC is the first step toward coordinated MVP-ADSP genetic investigations in ADRD. This supplement will fund the curation and mapping of MVP ADRD phenotypic data to be comparable with the harmonized phenotypes in ADSP-PHC, and deposit those data in the Data Commons according to ADSP-PHC schema. This includes (Supplementary Aim 1) ADRD diagnoses based on treatment codes and machine learning algorithms; (Supplementary Aim 2) vascular ADRD risk factors and other comorbidities; (Supplementary Aim 3) neuroimaging data; and (Supplementary Aim 4) neurocognitive test data. This work will also examine the demographics and medical comorbidities of MVP participants, thereby setting the stage for comparisons with diagnoses and other relevant endophenotypes in the ADSP-PHC. The proposed effort will boost the power for future mapping of genetic risk variants, especially in underrepresented groups, and will significantly enhance the ADSP’s efforts to unravel the heterogeneity of ADRD genetic risk, onset, symptomology, neuropathology, and progression, thereby improving the likelihood of identifying new targets for effective ADRD treatment in diverse populations.