Screening is one of the most widely used unit operations in mineral processing plants. In crushing circuits, the proper selection and sizing, optimization and their operation as efficient as possible are essential in terms of the performance and profitability of the crushing circuit and the whole plant. There are various empirical models used for the sizing and the performance prediction of the screening operation. Due to the high margin of errors during calculations and assumptions based on empirical models and owing to the continuous increase in the computational capacity of computers, the numerical methods such as discrete element method have been increasingly used for the simulation of screening. However, there is still a deficiency in the literature in the area of the pilot or industrial scale validation of simulation results. In this study, the effects of various design and operating variables (namely, feed rate, deck inclination, vibration frequency, amplitude and direction, aperture size) on the efficiency of screening are investigated by means of DEM simulation of industrial vibrating screens. Spherical and irregularly shaped particles (multi spheres) were used in the simulations. Additionally, the prediction capability of the simulator was revealed based on the validation tests conducted on a pilot scale vibrating screen.