Combustion, carbon monoxide (CO), Nitrous oxide (NO), formaldehyde (HCHO) and unburned methanol (CH3OH) emissions characteristics in a direct injection spark ignition (DISI) methanol engine with hydrogen addition ratio from 5% to 15% have been investigated numerically based on the detailed methanol oxidation reaction mechanism combined with the nitrogen oxides (NOx) reaction mechanism using the PREMIX code of CHEMKIN program with AVL FIRE software. Maximum cylinder pressure, maximum heat release rate and highest cylinder temperature increase and their corresponding crank angles advance with hydrogen addition from 0 to 15%. CO emission decreases and NO emission increases with increasing hydrogen addition ratio, whereas, formaldehyde and the unburned methanol significantly reduce with increasing hydrogen addition. Thus, hydrogen addition can provide a new way to address formaldehyde and unburned methanol unregulated emissions in a DISI methanol engine. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.