The 2004, 2007, and 2013 enlargement of the EU opened up free trade opportunities, increasing trade flows and demand for products of agriculture. On the one hand, the integration processes have intensified competition between countries, and on the other hand, they have created new opportunities for them. The aim of the study was to evaluate the effect of European integration on the competitiveness of the agricultural sector in countries that acceded to the EU in or after 2004. The assessment of the competitiveness of the agricultural sector was made using the following indicators: land and labour productivity in agriculture, importance of the agricultural sector in the economy of the EU countries, agricultural trade balance, importance of agricultural export in total export of the EU countries, trade coverage ratio, Grubel–Lloyd intra-industry specialization indicator, and Balassa comparative advantage indicator. The analysis was carried out from 2004 to 2020 with the Eurostat statistical database. The outcome of surveys implies that a gap still exists between the old and the new member states of the European Union (EU) in the efficient utilisation of their production factors, despite an increased dynamics of growth in labour productivity compared with the old member states, the so-called EU-15. The overall competitive position of all EU-13 countries in agricultural trade on the common EU market has improved; however, individual analysis reveals disparities between respective member states. In 2020, net exporters with comparative advantage were Hungary, Bulgaria, Lithuania, and Croatia, and net importers with comparative disadvantage included Poland, Czechia, Slovakia, Estonia, and Malta. Latvia and Romania improved their competitive position in agricultural trade