This study examines the how the adoption of computerised accounting information systems influence the financial performance of the public sector and then explore the mediating role of internal control system in the linkage between the drivers of CAIS adoption and financial performance of the public sector. Data was collected from the operators and controllers of CAIS of 227 local governments across the sixteen regions of Ghana using questionnaire as the main instrument. The structural equation modelling was employed to analyse the hypothesized relationships between the drivers of CAIS adoption and financial performance and the mediating role of internal control. The initial model specification considered sixteen measurement variables, but through the data reduction technique, factor analysis, four factors were identified as being the main determinants of CAIS adoption. Using these factors as exogenous constructs, it was found that, whiles cost of adopting CAIS and readiness to adopt CAIS significantly influence the financial performance of local government, CAIS complexities and data security cost and threat have no significant direct influence on financial performance. Also, internal control system mediates the relationship between CAIS complexities and financial performance, and then data security threat and cost, but internal control system does not mediate the relationship between cost of adopting CAIS and financial performance and then readiness to adopt CAIS and financial performance. On this basis, the study recommended interventions by government to improving technology adoption among local government such as ICT education, training, emphasis on strengthen internal controls and awareness creation programs among key controllers of the local government. Also, local government should consider CAIS technology on the basis of Software-as-a-service (SaaS), also known as cloud accounting in an attempt to deal with the cost of managing accounting information systems.