The objective of this study was to explore the feasibility and preliminary effectiveness of the Lifestyle-Integrated Functional Exercise for People with Dementia (LiFE4D) on health-related physical fitness, cognitive function, physical activity, and respiratory and upper limb functions. A randomized controlled pilot study was conducted (control group: usual care; experimental group: usual care and LiFE4D). The feasibility of LiFE4D was determined considering recruitment, protocol acceptability, adherence, and safety. Measures of health-related physical fitness, cognitive function, physical activity, and respiratory and upper limb functions were assessed at the baseline and 3 months. Twelve participants (8 [66.7%] female, 82 [72.2-84] years) were included, six per group. Recruitment was challenging. LiFE4D was acceptable with excellent adherence and no major adverse events. Cardiorespiratory endurance (effect size = 1.64, 95% confidence interval [CI; 0.33, 2.95]) and balance (effect size = 1.46, 95% CI [0.19, 2.73]) improved after LiFE4D. LiFE4D seems to be feasible and safe, and it shows potential to significantly improve the health-related physical fitness of people with dementia.