The STIM-PRADER study aims to assess the effectiveness of auricular vagal neuromodulation therapy (aVNT) on emotional, behavioral, and cognitive domains impaired in Prader-Willi Syndrome (PWS). Currently, no treatment exists that addresses the multiple alterations associated with this rare neurodevelopmental disorder that significantly impact patients and their families. We will investigate the effects of daily, four-hour aVNT stimulation over a nine-month period on (a) emotion regulation, including assessing the persistence of effects following stimulation; (b) executive functions, including inhibition, flexibility, planning, and updating information in memory; (c) hyperphagia; (d) depression; (e) quality of life; (e) and the threshold at which effects on these dimensions can be observed. We will conduct a longitudinal multicenter parallel randomized controlled single-blind exploratory trial. Twenty-four adults with PWS and 24 caregivers will be randomly assigned to receive either active or sham stimulation under identical conditions (four hours per day, seven days per week over nine months). The primary outcome, focusing on emotional control, will be assessed every two weeks for both participants and caregivers. Secondary outcomes (executive functions, hyperphagia, depression, and quality of life) will be measured at four time points: pre-intervention, at three months, six months, and at nine months. As this is the first multicenter randomized controlled trial investigating the effects of aVNT as a treatment in PWS patients, we anticipate witnessing improved emotional regulation and reduced eating disorders, along with enhancements in executive functions and quality of life in the active stimulation group. The findings from this project could support the development of broader therapeutic approaches for other conditions in which behavioral disorders and emotional processing deficits affect patients and their caregivers.