This research primarily focuses on isomorphic pressure as a significant reason for preparing comprehensive sustainability disclosure. This study also builds a comprehensive index of disclosing information in several sustainability reports along with the help of the Global Reporting Initiative (GRI). Moreover, the research involves content analysis for the quantity and quality of sustainability data. The data has been collected from the top 100 companies registered by the PSE (Pakistan Stock Exchange). As a methodology, we used the Tobit regression model to examine the isomorphic pressure to prepare the comprehensive sustainability disclosure. The findings of this research show that isomorphic pressure positively contributes to preparing comprehensive sustainability disclosure in Pakistan. This study assesses the comprehensive sustainability disclosure and the simultaneous effect of quantity and quality of sustainability reports for the period 2012-2017. It extends the literature through the lens of institutional theory by examining how isomorphic pressure is becoming a reason for companies to prepare comprehensive sustainability disclosures. The outcome of this study holds applicability for regulatory bodies, industry professionals, and academia.