Dielectrophoresis has been widely used to focus, trap, concentrate, and sort particles in microfluidic devices. This work demonstrates a continuous separation of particles by size in a serpentine microchannel using negative dielectrophoresis. Depending on the magnitude of the turn-induced dielectrophoretic force, particles travelling electro-kinetically through a serpentine channel either migrate toward the centerline or bounce between the two sidewalls. These distinctive focusing and bouncing phenomena are utilized to implement a dielectrophoretic separation of 1 and 3 mm polystyrene particles under a DC-biased AC electric field of 880 V/cm on average. The particle separation process in the entire microchannel is simulated by a numerical model.