Counties (poviats) undertake a variety of activities aimed at improving environmental quality and ensuring the sustainable management of natural resources. The aim of this paper is to examine the efficiency of these activities among the counties of the Wielkopolskie Voivodeship within the framework of the “Environmental Protection Program for the Wielkopolskie Voivodeship for 2016–2020.” Using the DEA method, we analysed the efficiency of pro-environmental activities across individual counties in 2015, before the program’s implementation, and in 2020, in its final year. A ranking of counties in terms of their environmental efficiency was constructed, changes in their positions between the two analysed periods were examined, and the Malmquist index was also calculated. The study found that the relative efficiency of individual counties increased over the analysed period. It also identified the counties showed the greatest improvement in environmental efficiency, and demonstrated that changes in productivity were predominantly endogenous in nature, resulting mainly from improvements in the efficiency of resource utilisation rather than technological progress.