A Research Report Submitted to Mzumbe University – Mbeya Campus College in Partial Fulfillment of the Requirement for the Bachelor Degree of Accounting and Finance (BAF- BS) of Mzumbe University.The study on the role of internal control system towards the performance of public sector was carried in Mbeya at SIDO. Specifically, the backward development in the public sector has been attributed to weaknesses in the Internal Control Systems in the public sector. Huge amount of money is lost due to Internal Control inadequacies and other criminal temptations, which to say the least, drains the nation’s meager resources with its far-reaching and attendant consequences on the development or even socio economic or political programs of the nation. Thus, public sector organizations do not have strong policies and systems to check these activities in the public sector The study use case study design to gather the information at the study area. Purposive sampling techniques was applied to select 14 respondents from the population. Primary data were collected directly from the respondents using structured interview and observation whereas secondary data were collected through a documentary review of sources including published and unpublished materials. The data collected were analyzed by SPSS version 16 and excel. The contribution of internal control system towards the performance of internal control system it enhances the comparison of reports with related performance of public sector, also internal control system has the task of ensuring appropriate access to and use of information systems that enables expenditure from different departments to be shown according to budget. Internal control system reduces the impact of unexpected misallocation and misappropriation events or even to avoid them altogether when facilitated with proper procedures to heads of departments and accountants. It is recommended that enhancing knowledge provision to employees would facilitate quality service provision in public sector.