The study brings attention to a significant problem: the gap in eco-efficiency between EU countries depending on the date of accession. This study aims to analyse eco-efficiency at the micro-level (farm) between two distinct groups of EU Member States: those that joined before 2004 and after 2004. The survey covered individual commodity farms dealing with field crops. The research used data from the Farm Accountancy Data Network from 2013 to 2020. The study uses input-oriented Data Envelopment Analysis (DEA) and the Malmquist productivity index. The study concludes that farms in countries that acceded to the EU before 2004 feature a higher eco-efficiency level. On the other hand, farms from the EU Member States that joined the EU at the expansion stage after 2004 have gradually reduced the distance, which is reflected by the increased dynamics of the eco-efficiency index in the period under review.