Background: To better manage patients with a wide range of mental health problems, general practitioners would benefit from diagnostically accurate and time-efficient screening tools that comprehensively assess mental illness. Therefore, the aim of this systematic review was to identify screening tools that either take a multiple-mental disorder or a transdiagnostic approach. As primary and secondary outcomes, diagnostic accuracy and time efficiency were investigated. Methods: The data bases MEDLINE, Embase, Cochrane Library, Psyndex and PsycINFO were searched. Studies reporting on multiple-mental disorder or transdiagnostic screening tools used in primary care with adult patients were included. Sensitivity, specificity, positive and negative predictive value served as measures of diagnostic accuracy. Time efficiency was evaluated by the number of items of a screening tool and the time required for its completion and evaluation. Results: Eleven studies met the inclusion criteria. The majority of screening tools assessed multiple mental disorders separately. A sub-group of screening tools took a transdiagnostic approach by examining the spectrum of mood, anxiety and stress-related disorders. One screening tool used internalised, cognitive/somatic and externalised dysfunction as transdiagnostic domains of mental illness. Mostly, a sufficient sensitivity and specificity was reported. All screening tools were found to be time efficient. Conclusion: The eleven identified screening tools can support general practitioners to identify patients with mental health problems. However, there was great heterogeneity concerning their diagnostic scope of psychopathology. Further screening tools for primary care are needed that target broad constructs of mental illness, such as transdiagnostic factors or personality dysfunction.