The subject of governance has become a pertinent issue for business, government, politics, and the general public. In
both the private and the public sectors, there is an increasing demand for good governance in terms of accountability
and transparency, and internal audit function within organizations has an important role to play in the achievement of
these objectives. This study therefore assessed the effects of internal audit function (IAF) on good governance in the
public sector in Nigeria. Primary data was obtained through the administration of structured questionnaire to
purposively selected respondents comprising Head of Internal Audit, Director of Finance and Supplies, and Head of
Local Government Administration, in 33 public sector organizations in Oyo State, Southwestern Nigeria. A total of 99
respondents participated in the study. IAF was measured by independence of internal audit system, scope of work,
professional competence, examination process, and management support, while quality of service, management of
public resources measured good governance. Data obtained was analysed using correlation analysis and multiple
regression technique. The results showed that the effectiveness of IAF in Nigerian public sector organisations was
moderate since internal audit system in the public organisations was not absolutely independent and professional
competence was limited due to the challenge of insufficient funds to successfully carry out its duties. Moreover, the
study revealed that IAF had significant and positive effect on the quality of service delivery and management of
resources in the public organisations. The study concluded that internal Audit function is a veritable tool for promoting
good governance in the Nigerian Public Sector. This study therefore recommended that there should be legal mandate in
public sector organisations that allows government information to be publicly published and special funds should be
made available to internal auditors as it would enhance effectiveness of internal audit function and boost good
governance in the organisations.