This work addresses the erosion performance of waste copper slag filled jute fiber reinforced polyester composites. The composites are prepared by two different fiber treatment methods such as sodium hydroxide (NT) and calcium hydroxide (CT) and the results are compared with the specimen prepared by untreated fiber (UT). The fiber dosage of 40% and the waste copper slag filler materials of 10% are used to prepare the composites. A compression molding machine with an optimum pressure of 17 MPa is used for the fabrication process. Erosion tests are conducted on an erosion test rig by varying the input process parameters such as impingement angle (30 degrees, 60 degrees, 90 degrees) and jet pressure (70, 100, 130 m/s). The experimental result shows that use of copper slag filler particles increased the interfacial bond between the matrix and fiber resulting to erosion prevention. A regression model has been developed for each composite to predict the future values. Further, the desirability analysis was performed and found that the CT composite with impingement angle at 90 degrees and jet velocity at 86.36 m/s could achieve lower erosion rate. Finally, the erosion mechanism of the eroded surface of the composite has been studied using scanning electron microscope and 3D surface profilometry images. (C) 2019 Elsevier Ltd. All rights reserved.