A Dissertation Submitted in Partial Fulfillment of the Requirements for the Award of Master of Science in Accounts and Finance (MSc A&F) of Mzumbe University.There is growing recognition of the important role of internal auditing in business risk management in organizations. This paper contains the results of a study conducted at National bank of commerce in Dar es Salaam in 2013. Organizations are entangled with myriad problems mitigating their effectiveness in conducting internal audit in Tanzania, notable among them are, inadequate competent audit staff, However, Inadequate fund, Lack of adequate material resources. This study therefore aimed to assess factors that affect the effectiveness of internal audit in business risk management in an organization. The study used both primary and secondary sources of data gathered through questionnaires and interviews. The study results reveal that there is a positive relationship between internal audit resources and competencies and internal audit effectiveness in managing risks in organization in Tanzania. It was also observed that the perception of other employees about the office of the internal auditor was not impressive. Due to their bad perception the auditing staff facing many challenges on their work some of them are as follows; Hatred from other staffs hence no co-operation with the auditor, Inadequate competent hands to audit the accounting books, Inadequate fund, Lack of adequate material resources, Overlap owing to responsibilities, Confronted from contractors/suppliers of services, Temptation to cover frauds, No time they are always in the office or on the road. .More specifically, this means there is a challenge on the organization management’s part to ensure internal audit effectiveness. The study recommends that organization must improve internal auditor’s independence, timely, adequate information access, and sufficient management support on education and on job training to expose internal auditors to new developments which could help in improving the effectiveness of internal auditing in their organization. Finally, internal auditors are advised to improve their communication skills so that the presentations they make are clear and understandable to their clients. Internal auditors must spend time in explaining to their clients what the internal audit is expected to achieve and how important contributions from the client are to that process