Cost and duration estimation process is important to be monitored and controlled in construction projects. Estimation variation from actuals presents a problem when attempting to complete a project on planned time and budget. Various studies cover project performance monitoring with different cost and time performance indices. Nevertheless, project monitoring techniques do not take advantage of the available data to assess the performance and accuracy of estimates developed by the estimation team. This research proposes using statistical process control (SPC) to assess the consistency and stability of the estimation of activities’ costs and durations. The proposed system calculates the deviation of the estimated costs and durations from the actual values. These calculations are the activities’ indices that are used to plot the control chart. The process capability analysis (PCA) is used to determine the accuracy deviation of the estimations from the organization’s targets. Results of the proposed system application to a real project determine the activities that have inaccurate costs and durations estimations. This result helps the estimation departments to analyze reasons for inaccurate estimations. The proposed system is an easy effective tool for continuous improvement to the performance of the estimation department.