This paper investigates the factors contributing to environmental laggardism within the European Union, using Greece as a case study. It moves beyond reductive explanations, such as the "Mediterranean syndrome," and single-variable analyses, instead situating the issue within the broader leader-laggard debate. The research employs a mixed-methods approach, integrating quantitative data on Greece’s EU environmental infringements from 2000 to 2022 with qualitative insights from 32 in-depth interviews conducted with key Greek environmental actors. Thematic analysis, guided by a structured codebook framework, identifies significant deficits in policy capacity as the principal drivers of laggardness. Specifically, systemic political, systemic operational, and organizational operational deficits—conceptualized by Wu, Howlett, and Ramesh (2015, 2018)—emerge as critical challenges. The findings suggest that the policy capacity framework provides a robust lens for evaluating the ability of states, organizations, and individuals to implement EU policies effectively. A detailed examination of Greece’s case not only reaffirms its status as an environmental laggard but also refutes the economic development and crisis hypotheses. This analysis offers valuable insights into the complexities of environmental policy implementation within the EU, advancing understanding of the structural and institutional barriers faced by laggard states.