In this study, an abrasive water jet machining process was used to evaluate the machinability of Hardox 400 steel, as one of the most widely used materials in the sheet metal industry. In this regard, surface roughness and geometrical tolerances (flatness, parallelism, and perpendicularity) were considered as the machining outputs, and water jet pressure, the weight percentage of abrasive particles, nozzle gap and feed rate were considered as the process input parameters. Followed by machining tests, the measurement of geometrical tolerances and surface roughness was performed through coordinate measuring machine (CMM) and surface roughness tester, respectively. The obtained results indicate that by the increase of jet pressure, decrease of feed rate, decrease of nozzle gap and increase of abrasives particles weight fraction, the surface quality improves and the geometrical errors reduce. Also, it was observed that the best surface roughness and geometrical tolerances have been obtained in the case of water jet pressure of 300 MPa, the feed rate of 10 mm/min, the abrasive weight percentage of 30% and nozzle gap of 1 mm. By repeating the experimental tests, it was shown that the relative error of the obtained results is less than 10%, which indicates the high repeatability of the results.