Over the last two decades, business communities worldwide put their increasing awareness on environmental or “green” issues. Companies start putting extra attention on taking care of their environmental issues while creating profit and improving financial performance. The conventional perception of environmental performance as mere additional costs imposed on companies has been challenged by studies on the relationship between environmental and financial performance, although results have been inconclusive. The purpose of this study is to examine the relationship between environmental and financial performance amongst companies listed in the Indonesia Stock Exchange (IDX). Indonesia is chosen as developing country, which is under-represented in existing studies on this theme. This study uses a quantitative research approach and will employ statistical correlation and crosstabs – chi square. The environmental performance is measured by the government of Indonesia’s environmental rating called “PROPER”, while the financial performance is measured by return on asset (ROA). Two other variables, namely company’s asset size and ISO 14001 certification are also included in the analysis. The results show that a company’s environmental performance is not significantly related either to ROA or to ISO 14001 certification. It is, however, positively related to the company’s asset size. This finding fails to support several previous studies that confirm the positive relationship between environmental performance, financial performance and ISO 14001 certification. On the other hand, it reaffirms previous studies that argue companies with bigger asset size tend to have a better environmental performance. This study enriches literatures on this theme by capturing the relationship between environmental performance, ROA, ISO 14001 certification and asset size in the context of a developing country.