Waterflooding is one of the most common techniques used to improve oil recovery. Although waterflooding has been extensively implemented in light oil reservoirs, only a few waterflooding studies and field tests have been conducted in heavy oil reservoirs. Therefore, the effect of various operating and reservoir parameters on the performance of waterflooding in heavy oil reservoirs is not well understood. This study presents the results of several series of displacement experiments and simulation studies evaluating different aspects of the waterflooding process in heavy oil reservoirs. The studies include evaluating effects of viscosity, water injection rate, permeability of porous media and wettability on relative permeability curves of heavy oil-water systems and ultimate oil recovery. The experimental study was conducted using a physical model and then a two-phase black oil commercial simulator (CMG/IMEXTM) was used to simulate waterflood experiments. The findings of this investigation provide important information of great interest to engineers, managers, and professionals working in the petroleum Engineering.