Over the years, the Financial Accounting Standards Board (FASB) and the International Accounting Standards Board (IASB) have made numerous changes to controversial leasing rules. The International Financial Reporting Standard (IFRS) 16 Financial Leasing Standard published by IASB has been implemented as of January 1, 2019 (In Turkey, this standard is published under the name of TFRS 16 by Public Oversight Accounting and Auditing Standarts Authority). The purpose of this paper is to analyze the impact of the new leasing standard on the financial statements and ratios of the firms and industries represented in the BİST 100 indice under a variety of assumptions. The financial statements and disclosures of the 63 manufacturing companies listed in BİST 100 are investigated. Under various assumptions; the effect of IFRS 16 on the financial statements and ratios is measured. In this context, it was assumed in 2017, companies used IFRS 16 instead of IAS 17. The related accounts and ratios were recalculated accordingly. Thus, it was possible to see the effect on the financial statements and financial statements items according to IAS 17 and IFRS 16. As a result of the calculations and analysis, decrease in income for the period; and increase in operating income before financial income/expense, operating income, financial expenses, total assets and total labilities are determined. And also, the findings indicate there is a decrease in ROA and net profit margin; increase in debt to asset and operating income margin. With the adoption of IFRS 16, the rights and liabilities related to the operating leases will be reported on the balance sheet. In this way, the comparability will increase and financial ratios will become more significant. This will also have an impact on strengthening the fair presentation of financial statements.