Background: Age-related changes negatively affect physical fitness, body composition, and executive function and produce a decrease in regucalcin level expression in blood. The square-stepping exercise (SSE) is a balance and lower-limb strength training programme used to prevent falls and stimulate cognitive function in older adults. This project aims to analyse the effects of SSE on executive function, regucalcin expression, fall prevention, body composition, and physical fitness in people over 65 years old. Methods: A randomized controlled trial will be conducted. A total of 90 older people over 65 years old will be recruited and randomly assigned to 2 groups: experimental (n = 45) and control (n = 45). The experimental group will perform an SSE-based intervention for 6 months (2 times per week), while the control group do not follow any treatment. Results: The main outcome will be balance, but other motor (body mass index, upper- and lower-limb strength, flexibility, and speed-agility) and cognitive variables (executive functions and attention) will be assessed. The expression of regucalcin levels will also be evaluated. Therefore, this project aims to analyse the effect of a 6-month SSE intervention on cognitive and motor competence, physical fitness, regucalcin levels, fall risk, and body composition in older people. If the intervention proves to be effective, it could be implemented in centres, entities, and associations specialized in elderly care.