Sustainability reporting involves the disclosure by corporate organizations on the positive and negative impacts of their activities on the economy and the general environment. This study examined the extent of sustainability reporting practices among Nigerian quoted companies. Four components of sustainability reports were considered—general disclosures, economic disclosures, environmental disclosures, and social disclosures. Data on the sustainability reporting practices of companies were extracted from the reports using content analysis based on the features of the 2021 version of Global Reporting Initiative (GRI). The findings show that the general disclosures have an average disclosure of 42.1%, the economic disclosures have an average disclosure of 23.5%, the environmental disclosures have an average disclosure of 15.5%, and the social disclosures have an average disclosure of 27.9%. Though there were generally poor disclosures of sustainability activities, the environmental activities disclosures were the least presented. In conclusion, the level of sustainability activities disclosures in Nigeria is still very low and could be classified as poor; there is great need for improvement. It is believed that the adoption of IFRS S1 and IFRS S2 will bring massive improvement to sustainability reporting in Nigeria.