The objective of this study is to determine the factors that explain the orientation, of the wine industry and at firm level in Portugal and Spain for adopting policies to improve sustainability, identifying similarities and differences between the two countries. The study focuses on two countries that account for a relevant part of the global vineyard surface area, wine production and wine exports. The database for the empirical analysis has been constructed through a survey conducted among wineries of the two countries during 2020 and 2021, for which a total of 568 valid responses were obtained. From the quantitative analysis, based on three Box-Cox left-hand-side models, it can be concluded that those wineries that invest the most in their growth and anticipate future challenges are more inclined towards adopting sustainability policies. The study also reveals notable differences between the two countries as the determinants that drive sustainability are more varied in the Spanish wineries than in those of Portugal.