Microwater droplet splitting and merging in a parallel-plate electrowetting-on-dielectric (EWOD) device have been studied numerically. The transient governing equations for the microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The interface between liquid and gas is tracked by a coupled level set (LS) and volume-of-fluid (CLSVOF) method. A continuum surface force (CSF) model is employed to model the surface tension at the interface. Contact angle hysteresis which is an essential component in EWOD modeling is implemented together with a simplified model for the viscous stresses exerted by the two plates at the solid–liquid interface. The results of the numerical model have been validated with published experimental data and the physics of droplet motion within the EWOD device has been examined. A parametric study has been performed in which the effects of channel height and several other parameters on the fluid motion have been studied.