Objectives: To study the effects of physical stimulation based on walking exercises, equilibrium and endurance on cognitive function and walking efficiency in patients with dementia. Methods: Randomized controlled trial including 31 subjects suffering from dementia (age: 81.8 ± 5.3 years). The intervention group (n = 16) benefited from a 15-week physical activity programme involving three 1-hour sessions per week. The control group (n = 15) did not practice any physical activities. Before and after rehabilitation, all subjects were evaluated with the Rapid Evaluation of Cognitive Functions test (ERFC French version) and walking analysis. Results: After the 15 weeks of rehabilitation, the subjects from the intervention group improved their overall ERFC score (p < 0.01), while those in the control group decreased their overall ERFC score. Interactions were also observed between walking parameters and groups (p < 0.01); the intervention group improved walking capacities through heightened walking speed, stride length and a reduction in double limb support time. Lastly, the subjects from the control group presented a reduction in both walking speed and stride length. Conclusion: This study shows that a physical activity programme can slow cognitive decline and improve quality of walking in elderly persons suffering from dementia.