Purpose The continuum of mental health/illness has been subject to scientific debate for decades. While current research indicates that continuum belief interventions can reduce mental health stigma and improve treatment seeking in affected populations, no study has yet systematically examined measures of continuum beliefs. Methods This preregistered systematic review summarizes measures of continuum beliefs. Following the PRISMA statement, three scientific databases (PubMed, PsycInfo and PsycArticles via EBSCOhost, Web of Science) are searched, instruments are described and discussed regarding their scope, and methodological quality. Results Overall, 7351 records were identified, with 35 studies reporting relevant findings on 11 measures. Most studies examined general population samples and used vignette-based measures. Schizophrenia and depression were most commonly examined, few studies focused on dementia, ADHD, OCD, eating disorders, and problematic alcohol use, or compared continuum beliefs across disorders. Validity was very good for most measures, but reliability was rarely tested. Measures mostly assessed beliefs in the normality of mental health symptoms or the normality of persons with such symptoms but rarely nosological aspects (i.e., categorical v continuous conceptualization of mental disorders). Conclusions Current research provides psychometrically sound instruments to examine continuum beliefs for a variety of mental disorders. While studies suggest utility for general population samples and mental health professionals, more research is necessary to corroborate findings, for instance, regarding age (e.g., in adolescents), gender, or type of mental disorder. Future research should also compare self-report ratings, and vignette-based measures, include measures of nosological concepts to fully grasp the continuum concept of mental illness. Preregistration PROSPERO: CRD42019123606.