<p>This study explores the influence of green intellectual capital (GIC) on the competitive advantage of Spanish wineries, focusing on the role of greening suppliers and green brand image in the GIC-competitive advantage relationship. The objective is to understand how the development of environmental knowledge and capabilities within organizations can translate into improved competitiveness through concrete mechanisms related to supply chain practices and brand perception. The empirical analysis is based on data collected from 196 Spanish wineries and examined using partial least squares structural equation modeling (PLS-SEM). This technique was selected due to its suitability for testing complex models with latent variables and mediating effects, and for its capacity to handle non-normal data distributions with relatively small samples. These findings have practical implications, as they underscore the strategic value of investing in green knowledge to foster collaboration with environmentally responsible suppliers and enhance brand positioning. The results confirm a positive and significant relationship between GIC and competitive advantage. Furthermore, they reveal that greening suppliers and green brand image partially mediate this relationship. This research makes an original contribution by addressing two gaps in the literature; on the one hand, it is the first empirical study to explore greening suppliers and green brand image as mediating variables in the GIC-competitive advantage relationship and, on the other hand, it applies this framework to the wine industry, a sector that has received little attention in this field despite its growing exposure to environmental pressures and its strategic relevance for the Spanish economy.</p>