This paper experimentally investigated the effect of hydrogen addition on the cold start performance of a methanol engine. The test was conducted on a modified four-cylinder gasoline engine. An electronically controlled hydrogen injection system was applied to realize the hydrogen port injection. The engine was started at an ambient temperature of 25 degrees C with two hydrogen flow rates of 0 and 189 dm(3)/s, respectively. The results demonstrated that hydrogen addition availed elevating the peak engine speed and cylinder pressure during the cold start. Both flame development and propagation periods are shortened after the hydrogen addition. When the hydrogen volume flow rate was raised from 0 to 189 dm(3)/s, HC, CO and total number of particulate emissions within 19 s from the onset of cold start were reduced by 68.7%, 75.2% and 72.4%, respectively. However, because of the enhanced in-cylinder temperature, NO emissions were increased after the addition of hydrogen. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.