Abstract Background Front-of-pack (FOP) nutrition labeling has been recommended by the World Health Organization (WHO) as one of a suite of measures needed to improve population diets. The voluntary Nutri-Score FOP labeling system, which was first implemented in France, was approved for implementation in Belgium by the Minister of Public Health in August 2018 and has been officially adopted in Belgium since April 1st 2019. We assessed the uptake of Nutri-Score by food retailers and manufacturers during the first year of implementation in Belgium. Main body In November–December 2019, pictures for 1781 products displaying Nutri-Score on the FOP were collected from the five biggest retailers, representing about 10% of products on the market in Belgium. About 90% of products displaying Nutri-Score on the FOP in 2019 were own-brand products from two major food retailers, while the few remainder were branded products. About 56% of products displayed Nutri-Score A or B while 26% of products displayed Nutri-Score D or E. Conclusion During the first year of implementation, > 1700 food products displayed Nutri-Score on the FOP in Belgium. While the majority of those products were healthier foods (Nutri-Score A&B), about one quarter of less healthy products (Nutri-Score D&E) already displayed Nutri-Score as well. In the meantime, all five biggest retailers, including discounters, have committed to display Nutri-Score on the FOP from 2020 onwards, which may increase pressure on other food manufacturers to improve uptake of Nutri-Score for branded products.