This study was on effectiveness of internal auditing in improving public sector management in Tanzania: A case of Institute of Adult Education. Specifically the study sought find out whether Internal Audit department in Institute of Adult Education is adequately staffed to perform its role effectively in such institution, examine the pattern and extent of internal audit involvement in IAE financial management activities and how that may influence IAE goals achievement an explore challenges facing internal audit in IAE and ways to overcome them. The study was conducted in Institute of Adult Education in Dar es Salaam. The sample population was 68. The study revealed that majority auditing staffs had degree in auditing, followed by those with diploma in auditing and masters degrees. On other hand study revealed that about 18 (28%) informants mentioned ensuring effective organization performance management and accountability as one way internal audit involved in IAE financial management activities. Others 13 (20.6%) said Coordinating the activities of and communicating information among board, external and internal auditors and management, 11 (17.4%) said secure completeness and accuracy of records in the institution. Additionally, about 9 (14.2%) said by detecting and preventing frauds and errors whereas only 6 (9.5%) said by assessing and monitoring risk that organization face and recommends ways forward and supervising all phase of budget cycle. Nevertheless, internal auditing faced several challenges including lack of appreciation of internal auditing function by management, inadequate funding, and lack of effective internal auditing committee and absence of risk management framework. It was concluded that internal auditing in IAE play an effective role in helping management in financial management. It was recommended that repetitive training, seminars and workshops should be arranged in order help the internal auditors in order to improve their working efficient.