Alzheimer’s disease is a devastating neurodegenerative disorder that poses a significant societal burden. Approval of anti-amyloid antibody therapies is a significant milestone for treatment that was enabled by the inclusion of biomarkers. The use of biomarkers in clinical trials for Alzheimer’s disease has enabled selective participant recruitment, improved treatment monitoring, and supported more rigorous trial designs. This review discusses emerging biomarkers associated with the biology of aging and their application in Alzheimer’s disease clinical trials. Aging is the primary risk factor for sporadic Alzheimer’s disease and is associated with biological processes implicated in disease development and progression. Novel therapies targeting these underlying biological aging processes are currently undergoing clinical development. Biomarkers that capture the biology of aging are integral to accelerating the development of these therapies. Current progress in biomarker development demonstrates efforts to capture the full spectrum of aging biology. Further work is needed to expand the range of biomarkers that enable comprehensive assessment of brain pathology and aid in prognosis, diagnosis, and measuring treatment response. Establishing a comprehensive arsenal of biomarkers will support strategic decision making and increase the likelihood of positive clinical trials and drug registration for the next generation of Alzheimer’s disease drugs targeting the biology of aging.