This study empirically investigates the effectiveness of international environmental agreements (IEA). Although there exists large number of empirical studies regarding IEA effectiveness, much of those studies focus on ratification decisions and regulated environmental behaviors at country level. This approach, however, is limited for investigating the attributes of different treaties and identifying factors affecting the success of IEA. To avoid this limitation, this study develops a treaty-level panel data including 14 environmental agreements adopted and entered into force last 20 years. This aggregated approach enables to look further insights regarding the attributes of each IEA, and identify the factors significantly affecting the effectiveness of agreements. From our results, several treaty-specific attributes are shown to be significant. Specifically, sanction for non- compliance is the most influential inducement for the effectiveness of IEA. A mechanism of financial assistance for less-capable developing countries is also found to be positive inducement, but mechanism of technical assistance is not significant at any statistical levels. Our results also indicate that involving larger number of countries, especially large-scale fast-growing developing countries such as BRICs, is another significant factor. Although this is not compatible with a strict sanction for non-compliance, introducing well-designed financial mechanism may be one of possible solutions for this incompatibility problem and making the IEA more attractive and effective.