The capacity to generate value-added services in order to acquire and retain loyal clients is one of the challenges facing the hospitality sector. For this reason and because of economic realities and government policies, an ever-growing number of hotels are formally adopting certified environmental practices such as the ISO 14001. In this article, we attempt to analyze the relationship between the implementation of a proactive environmental management tool, the ISO 14001 standard, and the generation of economic revenues in the Spanish hotel industry. Also considered are the possible effects on the business results of moderating factors such as company size and the market segment where the hotel operates. Empirical economic information on 2,116 Spanish hotels was obtained from the SABI database (Iberian Balance-Sheet Analysis System) for the year 2008, during which 108 properties had ISO 14001 certification. Quantitative analysis techniques showed significant differences in the economic performance of ISO-certified hotels and those not certified, particularly for urban and beach hotels. The results showed influence of both company size and organizational factors on revenue. Only small rural hotels saw no difference in revenues due to the presence or absence of ISO certification.