Hydrogen has been known as a clean and suitable fuel to replace conventional fossil fuels. One of the common hydrogen production methods is using water electrolysis process. This method produces oxygen as well as hydrogen by ratio of 1:2. The aim of this work is to investigate the effects of inlet air enrichment by adding produced hydrogen and oxygen to an internal combustion engine. For this purpose, an electrolysis system consisting of four cells have been built and the produced gas mixture was transferred to the inlet manifold of the engine via a rubber hose. The experimental results show that adding hydrogen and oxygen to the inlet air under the full load can cause reduction in CO and HC by 21% and 19% respectively, and increases power and torque by 5.5% under similar condition.