This paper examined the effect of capital structure on performance of Non-Bank Financial Institutions in Nigeria. The study employs annual time series data covering the period 2010-2019 obtained from the financial statements of 10 Insurance companies listed on Nigerian stock exchange which is the proxy for non-bank financial institutions. In carrying out the study, debt to asset ratio, equity to asset ratio, company size and asset quality are the proxies for the independent variable (Capital structure) while Return on Equity (ROE) served as the dependent variable. The data collected were analyzed using Ordinary Least Square (OLS) Technique. Other test conducted was stationarity/unit root test. E-view 9.0 was used to analyze the data, test hypothesis and the results obtain indicated among others that Debt to Asset Ratio has a positive and significant influence on the return on investment of the shareholders of the ten (10) insurance companies. The paper concluded that decisions regarding capital structure are very important because they have consequences on the ability of the company to grow, fund operations and new projects at a lower cost, increase returns for shareholders and stay in business, as wrong capital structures may lead to bankruptcy. The study therefore recommended that Insurance companies should pay special attention to firm’s leverages in determining their optimal capital structure. Insurance companies should also take into cognizance the amount of leverage incurred because it is a major determinant of firm’s performance.