Corporate Social Responsibility (CSR) activities are recognized as one of legitimacy strategies of companies to build a reputation. Ethical tax management strategy, in this context, is regarded part of companies' responsibilities to the stakeholders. Literature on the relationship between CSR activities and unethical tax management activities called as tax aggressiveness behaviors, nevertheless, is still inconclusive. Filing the gap of previous literature on CSR activities and tax aggressiveness behaviors, this study investigates the role of risk management systems in moderating the effect of CSR activities on tax aggressiveness behaviors. Having a sample of Indonesian listed companies during 2013 - 2015, this study shows a negative relationship between CSR activities and tax aggressiveness behaviors in companies, meaning that the higher CSR activities leads to the lower companies' tax aggressiveness behaviors. This study also found that risk management systems have role in moderating the relationship between CSR activities and tax aggressiveness behaviors, that are risk management systems weakens the negative effect of CSR activities on tax aggressiveness behaviors. The results bring an implication on the importance of companies' reputation to be legitimate, so the role of regulators become very important. This study contributes to the literature by taking the risk management systems into account in the relationship between CSR activities and tax aggressiveness behaviors, completed by CSR index improvement that reflects the current GRI G4 and risk management systems index improvement that relate to CSR and/or taxation based on Risk Oversight category in ASEAN CG Scorecard.