The present research examines both the relationship between green innovation and green entrepreneurship and the mediating role of firm strategies in the relationship between green entrepreneurship, green innovation, and competitive advantage. A total of 225 managers responsible for the environmental strategy of medium and large-sized firms operating in Greece were used as a sample for the study. To measure the research variables, a structured questionnaire was used. The collected data were analyzed using descriptive and inductive statistics, including principal components analysis, correlation analysis, a multivariate generalized linear model, and a structural equations model. The empirical results indicate a positive influence of green entrepreneurship in green product innovation and green process innovation. Furthermore, the mediating role of firm strategies in the relationship between green entrepreneurship, green innovation, and competitive advantage is confirmed.