Most of the prior literature focused on the scope, dimensions, importance, and business case of Corporate Sustainability (CS). A few studies also addressed the successful adoption or implementation of CS. Therefore, this study, by following the sequential process of stakeholder theory, adopts a holistic approach to inquire the impact of integrated management system (IMS) on CS and Firm Financial Performance (FFP). Besides investigating the link between CS and FFP, the study also theorizes the unique mediation of CS in the bonding between IMS and FFP. By employing ordinary least squares (OLS) and two-stage least squares (2SLS) to data collected through content analysis from a sample of 23 top companies listed in the real estate and construction industry on Bursa Malaysia from 2011 to 2016, it is revealed that IMS is a significant positive predictor of CS and all of its dimensions. Also, the study found the novel mediation of CS in the relationship between IMS and FFP (share market price). Besides contributing to the literature, the study also offers many empirical insights for the industry, regulatory bodies, and other stakeholders of developing countries, especially Malaysia.