A substantial proportion of the adult and aging population are affected by hypertension, which presents a significant risk for vascular cognitive impairment and late-life dementia. Prevention of dementia in the aging population is still an unmet target, and extensive research all over the world addresses the many pathogenetic mechanisms of hypertension-associated dementia. Previous excellent reviews from time to time already updated the results in the field for those who are only marginally involved in this topic. The present review is a further update, it summarizes in depth many new papers and provides a wide view of the fields of research in this area. Most importantly, there are new hints, poorly examined in previous revisions, such as the role of cerebral immune dysregulation, neuroinflammation, neurodegeneration, amyloid deposition, Alzheimer pathology, parallel analysis of these parameters in animal models and humans, and new ways of neuroimaging assessment. It has the merit of balancing hemodynamic, cellular, and biochemical mechanisms that are all equally relevant to understand how hypertension still represents one of the most insidious conditions that challenge brain health. Identification of each step may help to define strategies targeting the cerebral blood flow regulation, the immune system, or clearance pathways in the brain, which can be combined with already-existing antihypertensive therapy, mainly focusing upon hemodynamic effects.