Since maintenance plays a key role in a companyʹs overall performance, the main goal of this study was to provide a managerial tool for constantly monitoring and improving maintenance KPIs. This was achieved by designing and implementing a Computerized Maintenance Management System (CMMS) in an Iranian mid-size plant, manufacturing power plant utilities. In this study, CMMS software was developed and deployed in order to both monitor and optimize safety and maintenance KPIs. Selected KPIs were measured yearly; before, during and 12 and 24 months after intervention. Longitudinal Data Analysis and Mixtur Model were employed to compare the improvement trend of KPIs. Results show that at the end of the intervention year, KPIs other than Mean Time to Repair (MTTR) improved. Moreover, the improvement trend of the KPIs other than MTTR continued even 12 months after intervention was stopped. Similarly, although the "LWD" safety KPI had an overall improvement, comparing its figure before and after intervention, there was a significant decrease during the last 6 months of intervention. After the deployment of the CMMS, MTTR KPI increased surprisingly. Furthermore, the decrease in the "LWD" KPI revealed that off-the-job safety has a key role.