IT is often considered to be a driving force or success factor for firms’ agility. The universal precondition related to this statement is the fact that firms putting a great effort in IT can be more agile than their competitors. Paradoxically, IT that helps firm strategies may be a threat or may limit firms’ ability that reacts to business opportunities. That is, whether IT helps or influences to firms in various ways, issues related to firms’ agility has not been resolved yet. Therefore, this study proposes the point that acceleration and hindrance; directly opposing factors; between IT and agility has been frequently observed and attempts to theorize the relationship between these two factors. In addition, the lack of agility may severely restrict firm performance. Such agility may be influenced by various internal and external factors. Therefore, to effectively link the influences of firms’ agility performance that plays an important role in gaining competitive advantage for firms, this study examines the required types of agility and investigates the influences and the process it goes through. The current study focuses on two research questions as follows. First, is there a positive relationship between IT capability, firm agility, and firm performance? Second, to what extent does organizational support structure positively or negatively moderates the link between IT capability and firm agility? To answer these questions, firms’ agility is conceptualized into customer agility, partner agility, and operational agility. Moreover, organizational supporting structure suggested in the study includes training, online support, help desk support, and change management support. To test the proposed hypotheses, this study used SmartPLS 2.0 as the main tool for analyzing the collected data from 161 responses in various industries and positions. The results show that IT capability positively influenced firm agility and that firm agility significantly influences firm performance. However, it was identified that there was a subtle difference in proving moderating effect of organizational supporting structure. While IT capability significantly moderated the influence of firm agility according to the degree of training and change management support, online support and help desk support was partially influenced. Based on the findings, this study argues that in volatile markets, an effective model of IT governance in managing business is necessary to provide superior agility and adaptation. The findings of this study also suggest theoretically, perspective implications that show evidences in the early stages of agility studies. Practically, this study provides specific insights that can be a fine guideline contributing in decision-making related to IT of firms.