In this study, it was examined whether financial performance is an indicator that is adequate to be included in the Sustainability Index. For this purpose, the BIST 30 companies which were assessed for the period of November 2014-October 2015, the BIST 50 companies which were assessed for the period of November 2015- October 2016 and 63 companies which were assessed for the period of November 2016-October 2017 were selected as samples of the study. Financial performances of companies except financial companies in the sample were analyzed by ARAS (Additive Ratio Assesment) method using 10 financial ratios (Working Capital Turnover, Fixed Asset Turnover, Net Profit Margin, Equity Profitability, Asset Profitability, Current Ratio, Financing Ratio, Leverage Ratio, Investment Rate and Fixed Asset / Total Capitalization). The ranking obtained as a result of the evaluation was compared with the companies in the Sustainability Index. The estimated percentages were found as 45% (5/11), 64% (14/22) and 74% (25/34) respectively in terms of the examined periods of time. As a result, it has been determined that financial performance can be a sole indicator that is adequate to be included in the index.