Restless legs syndrome (RLS) is a highly prevalent condition that significantly disrupts sleep and causes reduced quality of life. While previous RLS research has mainly focused on the pharmacological treatment, this study presents the first instrument to measure self-care, the RLS-Self-care Behaviour questionnaire (RLS-ScBq). Self-care, defined as an active decision-making process, can empower patients to effectively participate in their own healthcare through awareness, self-control, and self-reliance to cope with their disease. Self-care can in a RLS context include actions such as physical exercise, meditation, and massage. Hence, the aim of this study is to explore the psychometric properties of the RLS-ScBq in patients with RLS. A cross-sectional design, including 788 patients with RLS (65% women, mean age 70.8 years, [standard deviation (SD) =11.4]) was used. Sociodemographics, comorbidities, and RLS-related treatment data, including insomnia symptoms (i.e., Insomnia Severity Index), daytime sleepiness (i.e., Epworth Sleepiness Scale) and RLS symptoms (i.e., RLS-6 scale) were collected. The validity and reliability of the RLS-ScBq were investigated using exploratory factor analysis and Rasch models. The two-factor solution (i.e., physical, and mental actions) showed an explained variance of 32.33% for The Self-care Behaviour Frequency part and 36.28% for The Benefit of Self-care Behaviour part. The internal consistency measured by Cronbach's α was 0.57 and 0.60, and McDonald's ω was 0.60 and 0.67, respectively. No differential item functioning was identified for gender, age, insomnia, daytime sleepiness, or RLS severity. The eight-item RLS-ScBq can serve as a tool enabling healthcare personnel to explore use and benefit of self-care activities in patients with RLS.