The paper examined the influence of internal control systems on financial performance of Nigeria’s construction firms. It utilized ridge regression to analyze data from a self-administered questionnaire administered to 305 employees at a company. Internal control had a strong positive impact on financial performance, as evidenced by an R2 of 82.92 percent. In the majority of cases, internal control had positive and statistically significant effects and correlations with financial performance. The positive effects of the control environment and risk assessment were statistically insignificant. It suggests upgrading the control system; the control system must be present and functional.