Rationale: Aspiration is a common sequela post stroke as a result of oropharyngeal dysphagia. It is primarily managed using the poorly empirically supported intervention of thickened liquids. Where evidence is limited, clinicians may rely on clinical practice guidelines to support decision making. The purpose of this systematic review and narrative synthesis was to evaluate the evidentiary bases of recommendations made by stroke clinical practice guidelines regarding the thickened liquids intervention. Methods: A systematic review was conducted on stroke clinical guidelines retrieved via searches conducted across a range of databases including Academic Search Complete, CINAHL, MEDLINE, and the Cochrane Library as well as through association websites. Guidelines were eligible for inclusion if they focused on adult stroke populations, made recommendations relating to the thickened liquid intervention and were published between January 2010 and December 2018. Four independent reviewers rated methodological quality using the AGREE-II instrument. Intervention recommendations were extracted and analysed using the Criteria for Levels of Evidence Reported from the Canadian Stroke Best Practice Recommendations and a novel framework examining the appropriateness of the supporting evidence.