The optimization of investment in assets in order to achieve a satisfactory return on asset and return on equity is a major problem being suspected by the researcher in the manufacturing industry in Nigeria. This study is to examine the effect of asset growth and financial performance of manufacturing firms in Nigeria.Thirty-two (32) manufacturing firms were selected from Nigeria Exchange Group (NGX), and secondary data was collected from the firms for a ten-year period (2013 – 2022). The data were analyzed using Descriptive analysis and robust PanelRegression analysis for correcting multicollinearity and heteroscedasticity. Non-current assets growth, current assets growth, net assets growth, and total asset growth were used as proxies for asset growth (independent variables), while return on assets (ROA) and return on equity (ROE) were used as proxies for financial performance (dependent variable). The result shows that the non-current assets growth rate and current asset growth have a significant negative effect on the ROA of manufacturing firms in Nigeria. However, the outcome is insignificant when financial performance is proxied as ROE. Findings also show that total asset growth has an insignificant effect on ROA and ROE. On the other hand, findings revealed that while net asset growth is insignificant to ROA, the outcome is significant and negative to ROE.The study concludes that increasing non-current, current assets, and net current asset growth can strain financial resources, leading to diminished performance in manufacturing firms. Based on this, the study recommends that Manufacturing firms should strive for a balanced approach to non-current asset growth, considering both short-term financial implications and long-term strategic objectives.