This study is to evaluate the relationship between assets growth rate and financial performance of manufacturing firms in Nigeria. Six (6) firms were selected from the twenty two (22) manufacturing firms listed on the Nigeria Stock Exchange Market (NSE) and secondary data collected from the firms for ten years period (2006 - 2015). The data were analyzed using Pearson Product Moment Correlation Matrix and Multiple Regression whereby the effects of the independent variables on the dependent variable were tested. Non-current assets growth rate, current assets growth rate and net assets growth rate were used as proxies for firm growth (independent variables) while profit after tax was used as proxy for financial performance (dependent variable). Result shows that non-current assets growth rate and net assets growth rate of manufacturing firms in Nigeria positively and strongly related with the profit after tax of the firms for the period of 2006 - 2015, while current assets growth rate positively and weakly related with the profit after tax of the firms for the period. The implication is that profit after tax grows as the non-current asset base of the firms grows. It was recommended that manufacturing firms in Nigeria should increase their non-current assets and net assets value by increasing their total assets and reducing the components of their current liabilities; also that the firms should increase their current assets, but should keep it at an optimum level that will ensure that maturing short-term business obligations are met to avoid keeping excess idle funds.