There is evidence from observational studies that increasing physical activity may reduce the risk of cognitive decline in older adults. Exercise intervention trials have found conflicting results. A systematic review of physical activity and exercise intervention trials on cognition in older adults was conducted. Six scientific databases and reference lists of previous reviews were searched. Thirty studies were eligible for inclusion. Articles were grouped into intervention–outcome pairings. Interventions were grouped as cardiorespiratory, strength, and multicomponent exercises. Cognitive outcomes were general cognition, executive function, memory, reaction time, attention, cognitive processing, visuospatial, and language. An eight-member multidisciplinary panel rated the quality and effectiveness of each pairing. Although there were some positive studies, the panel did not find sufficient evidence that physical activity or exercise improved cognition in older adults. Future research should report exercise adherence, use longer study durations, and determine the clinical relevance of measures used.