The objectives of this study were to discover the effectiveness of the environmental accounting on the financial information quality classified by the population characteristics and the organization sustainability of businesses certified by ISO 14001 in Thailand. The data were collected from 200 Finance and Accounting directors or managers of businesses certified by ISO 14001 in Thailand through the questionnaire as a research instrument. Statistics used in the data analysis included frequency percentage mean standard deviation multiple correlation analysis and multiple regression analysis. The results showed that the effectiveness of environmental accounting regarding in the aspect of the reliability of the data reporting was significantly related to the quality of financial information and corporate sustainability. In addition the quality of financial information was also significantly related to the organization sustainability which included the addition of business value competitive ability and the organization image.