Dissertation (MA Business Administration)Scholars and institutions have illuminated that the internal control system is important to control fraud and ensure financial performance in the organizations. This study illustrates this importance using the findings of the assessment made to know the effect of the internal control system on financial performance in Tanzania one mining company. The study examined the effects of control environment on financial performance, risk assessment on financial performance, the control activities on financial performance and internal auditing on financial performance. The respondents of this study were 51 who were purposively sampled from the top and middle level of Tanzanite one mining company staff. Data were analysed using multiple regression analysis. The findings of the study revealed that control environment, risk assessment, control activities and internal auditing had a positive and significant effect on financial performance of the mining company at 5% significance level. The internal control system had a positive and significant influence on financial performance. Following these findings, it concluded in this study that the control environment, risk assessment, control activities and internal auditing are important in improving financial performance of an organisation. This follows from the fact that internal control system helps the mining company to arrest fraud perpetration. The study recommends the Company to establish regular management and performance audits which are important to identify the areas with underperformance. Also, the government should offload some of its interest to private enterprises with a view to minimize political influence in decision making