Physical activity shows promise as a modifiable lifestyle intervention to benefit pathological symptoms of dementia. However, little is known about the factors associated with participation in physical activity in community dwelling adults with dementia. A systematic review was undertaken to identify physical activity correlates. Two independent reviewers searched major electronic databases and extracted data on studies reporting quantitative correlates of physical activity participation in community dwelling adults with dementia. Physical activity correlates were analysed using the summary code approach within the socio-ecological model. Out of a potential of 118 articles, 12 met the eligibility criteria encompassing 752 participants. We conducted secondary analysis on 9 data sets. Increased energy intake, resting metabolic rate, fat free mass, gait speed, global motor function, overall health related quality of life (HRQOL), physical HRQOL, higher levels of social functioning and reduced apathy were positively associated with physical activity. Taking ≥ four medications, dizziness, lower ADL function, a history of falls, less waking hours in the day, more autonomic problems and delirium were negatively associated with physical activity. Increasing age and lower global cognition were not consistently associated with physical activity participation. It is surprising that increasing age and lower global cognition do not appear to influence physical activity participation. All significant correlates should be confirmed in prospective studies with particular focus on the relationship of physical activity and gait speed, ADL function, falls history and dietary intake and the progression of frailty and nursing home admission as a priority.