Purpose The purpose of this study is to examine how the level of attributes of the internal audit function relates to the effectiveness of internal audit services in local government authorities (LGAs) in Tanzania. Design/methodology/approach Data have been collected through a survey whereby 510 respondents from LGAs in Tanzania through their Heads of Internal Audit Functions, Internal Auditors and Chairpersons of Audit Committees respond to the questionnaire. The data were subjected to principal component analysis and exploratory factor analysis to reduce the set of items and to provide continuous scores for use in multiple regression analyses. Findings The findings reveal that audit quality; organization setting and auditee attributes have a significant positive influence on the effectiveness of internal audit services in LGAs in Tanzania. Research limitations/implications The study covered only LGAs in Tanzania. Future research in this field should address the gaps identified in the study. Practical implications This paper highlights areas that need management attention on the improvement of the effectiveness of internal audit units. Originality/value This paper contributes to the literature of both internal auditing and management studies by linking the level of attributes of internal audit function which are audit quality, organization setting, auditee attributes and effectiveness of internal audit services in Tanzania.