Introduction: Mild Neurocognitive Disorders (mNCD) are characterized by a subtle decline in cognitive performance. Discourse analysis is a research method that investigates the verbal production of patients and has been used to screen for subtle cognitive impairment. Studies using discourse analysis are, however, rarely replicated. One reason for this is likely to be the lack of consistency across studies regarding the selection and definition of relevant linguistic features. The goal of this review is to identify reliable linguistic markers for the detection of subtle cognitive impairment in connected speech, and generate hypotheses associating these markers with underlying cognitive functions in a given discourse context. Methods and analysis: Following the PRISMA guidelines, we will conduct a systematic review including five databases: PubMed, ScienceDirect, Embase, Web of Science, Google Scholar. We will include articles targeting a population of patients with subtle cognitive impairment, such as Mild Cognitive Impairment. Eligible articles will include at least one connected speech task and an analysis of linguistic features in this task. The data will be classified according to study population, connected speech task, analysed linguistic features, and methods used to compare cases and controls. PROSPERO registration number: CRD42023394729.