Background: Frailty is a highly prevalent condition in old age leading to vulnerability and greater risk of adverse health outcomes and disability. Detecting and tackling frailty at an early stage can prevent disability. The purpose of this study is to evaluate the effectiveness of a multifactorial intervention program to modify frailty parameters, muscle strength, and physical and cognitive performance in people aged 65 years or more. It also assesses changes from baseline in falls, hospitalizations, nutritional risk, disability, institutionalization, and home-care. Methods/design: The current study is a randomised single-blind, parallel-group clinical trial, with a one and a half year follow-up, conducted in eight Primary Health Care Centres located in the city of Barcelona. Inclusion criteria are to be aged 65 years or older with positive frailty screening, timed get-up-and-go test between 10 to 30 seconds, and Cognition Mini-Exam (MEC-35) of Lobo greater than or equal to 18. A total of 352 patients have been equally divided into two groups: intervention and control. Sample size calculated to detect a 0.5 unit difference in the Short Physical Performance Battery (Common SD: 1.42, 20% lost to follow-up). In the intervention group three different actions on frailty dimensions: rehabilitative therapy plus intake of hyperproteic nutritional shakes, memory workshop, and medication review are applied to sets of 16 patients. Participants in both intervention and control groups receive recommendations on nutrition, healthy lifestyles, and home risks. Evaluations are blinded and conducted at 0, 3, and 18 months. Intention to treat analyses will be performed. Multivariate analysis will be carried out to assess time changes of dependent variables. Discussion: It is expected that this study will provide evidence of the effectiveness of a multidisciplinary intervention on delaying the progression from frailty to disability in the elderly. It will help improve the individual's quality of life and also reduce the rates of falls, hospital admissions, and institutionalizations, thus making the health care system more efficient. This preventive intervention can be adapted to diverse settings and be routinely included in Primary Care Centres as a Preventive Health Programme.