Abstract Objective: To investigate to what extent promotions in Dutch supermarket sales flyers contribute to a healthy diet and whether there are differences between supermarket types. Design: A cross-sectional study investigating promotions on foods and beverages (n 7825) in supermarket sales flyers from thirteen Dutch supermarket chains (8-week period), including ten traditional, two discount and one organic supermarket chain(s). Promoted products were categorised by food group (e.g. bread), contribution to a healthy diet (yes/no), degree of processing (e.g. ultra-processed), promotion type (temporary reduction in price, volume-based promotions or advertised only) and percentage discount of price promotions. Differences between supermarket chains in the degree of healthiness and processing of products and the types of price promotions were investigated. Results: In total, 70·7 % of all promoted products in supermarket sales flyers did not contribute to a healthy diet and 56·6 % was ultra-processed. The average discount on less healthy products (28·7 %) was similar to that of healthy products (28·9 %). Less healthy products were more frequently promoted via volume-based promotions than healthy products (37·6 % v. 25·4 %, P < 0·001). Discount supermarket chains promoted less healthy (80·3 %) and ultra-processed (65·1 %) products more often than traditional supermarket chains (69·6 % and 56·6 %, respectively). Conclusions: The majority of promoted products via supermarket sales flyers do not contribute to a healthy diet. As promotions are an important determinant of food purchasing decisions, supermarkets do not support healthy choices. Future studies should identify barriers that withhold supermarket chains from promoting more healthy foods in supermarket sales flyers.