The value of proactive environmental strategies to achieve and maintain competitive advantages in the business sphere has been widely acknowledged in recent years. However, mixed results can still be found regarding the determinants and consequences of the implementation of such practices. This study investigates the determinants of environmental proactivity in Spanish wineries, focusing on the role of company size in linking internal motivations and stakeholder pressure with proactive environmental strategy using the natural resource‐based view. So far, no research of this type has been carried out for the Spanish wine sector. A structural equation model is proposed based on partial least squares applied to a sample of 251 wine companies to evaluate both the direct relationships and the moderating effect. The study identifies internal motivations, community pressure, and regulatory pressure as determinants of proactive environmental strategy. Company characteristics play an essential role in decision‐making when dealing with environmental issues proactively. Small companies tend to be more influenced by internal motivations, while larger companies are driven to undertake environmental actions based on external pressures. Additionally, we found that managers who take a proactive approach to environmental protection can achieve financial rewards. These findings provide important implications for both policymakers and managers by offering new theoretical and empirical insight into how proactive environmental strategy affects financial performance in the case of Spain's wine companies. [EconLit Citations: O31, Q55, C30].