BACKGROUND: With the increase in life expectancy, age-related cognitive decline has become a prevalent concern. Physical activity (PA) is increasingly being recognized as a vital non-pharmacological strategy to counteract this decline. This review aimed to (i) critically evaluate and synthesize the impact of different PA and exercise modalities (aerobic, resistance, and concurrent training) on cognitive health and overall well-being in older adults, (ii) discuss the influence of exercise intensity on cognitive functions, and (iii) elucidate the potential mechanisms through which PA and exercise may enhance or mitigate cognitive performance among older adults. MAIN BODY: An exhaustive analysis of peer-reviewed studies pertaining to PA/exercise and cognitive health in older adults from January 1970 to February 2025 was conducted using PubMed, Scopus, Web of Science, PsycINFO, and MEDLINE. There is compelling evidence that aerobic and resistance training (RT) improve cognitive function and mental health in older adults, with benefits influenced by the type and intensity of exercise. Specifically, moderate-intensity aerobic exercise appears to bolster memory, executive functions, and mood regulation, potentially through increased cerebral blood flow, neurogenesis, and production of brain-derived neurotrophic factors in the hippocampus. Moderate-to-high-intensity RT acutely enhances visuospatial processing and executive functions, with chronic training promoting neurogenesis, possibly by stimulating insulin-like growth factor-1 and augmenting blood flow to the prefrontal cortex. Findings related to the effects of concurrent training on cognitive function and mental health are heterogeneous, with some studies reporting no significant impact and others revealing substantial improvements. However, emerging evidence indicates that the combination of concurrent training and cognitive tasks (i.e., dual tasks) is particularly effective, often outperforming aerobic exercise alone. CONCLUSIONS: Regular aerobic and RT performance is beneficial for older adults to mitigate cognitive decline and enhance their overall well-being. Specifically, engaging in moderate-intensity aerobic exercises and moderate-to-high-intensity RT is safe and effective in improving cognitive function and mental health in this demographic. These exercises, which can be conveniently incorporated into daily routines, effectively enhance mental agility, memory, executive function, and mood. The findings related to concurrent training are mixed, with emerging evidence indicating the effectiveness of combined concurrent and cognitive tasks on cognitive health and well-being in older adults. Key Points - Moderate-intensity aerobic exercise is associated with significant improvements in cognitive function, mood regulation, and overall well-being in older adults. These benefits are linked to structural and functional changes in the brain such as increased hippocampal volume and elevated levels of brain-derived neurotrophic factor. - Moderate-to-high-intensity resistance training, both in acute and chronic forms, enhances cognitive performance in older adults, particularly in executive functions and visuospatial processing. Cognitive benefits, including improvements in information-processing speed, attention, and memory, can be sustained through regular training. - The effects of concurrent resistance and aerobic training on cognitive function in older adults are mixed. However, combining concurrent training with cognitive tasks (i.e., dual-task training) is particularly effective and often outperforms aerobic exercise alone. - Cognitive and well-being improvements from aerobic and resistance training are mediated by mechanisms such as increased cerebral blood flow and oxygen delivery, enhanced neurogenesis, reduced oxidative stress and inflammation, and positive hormonal changes. - While the optimal exercise dosage for promoting cognitive health in older adults remains undetermined, empirical evidence indicates a positive correlation between increased exercise dosage and cognitive health improvements.