Cognitive aging describes the changes in mental abilities that occur with increasing age. Although experts disagree on the core underlying processes involved, one factor that links many factors associated with cognitive aging is neuroinflammation. Markers of inflammation are associated directly with deficits in cognitive function and with diseases that are risk factors for cognitive decline. Neuroinflammation is also associated with depression and may account for the complex interaction of depression and cognition in older adults. Interventions that reduce inflammation may improve cognition. Understanding how neuroinflammation affects cognition may provide directions for useful interventions to prevent or treat cognitive decline in older adults.