Purpose: To assess the methodological quality of all relevant and recent European clinical practice guidelines (CPGs) for advanced oesophageal and gastric cancers, and to synthesise their recommendations on the use of chemotherapy.Methods: We searched PubMed, EMBASE, guidelines repositories, and other sources from 2010 onwards. We appraised quality using AGREE-II and AGREE-REX.Results: 11 CPGs were included (five high, five low, and one moderate quality). Most guidelines showed deficiencies in the domain “applicability”, with only three scoring above 60%. Nine did not report having sought the views and preferences of the target population. The lowest scores for AGREE-REX were item Values and Preferences of Target Users (1.6; SD 1.3), and item Values and Preferences of Policy/Decision-Makers (1.8; SD 1.7). The domain Clinical Applicability got the highest score and the domain Implementability got the lowest.Conclusions: An urgent area of research is how to develop credible and implementable recommendations on the clinical use of CT for advanced oesophageal and gastric cancer. Systematic review registration: PROSPERO (CRD42021236753).