Despite the increase in vehicle electrification in recent years, the transport sector is still a major contributor to the rise in global carbon dioxide (CO2) emissions. Using dynamic product lifecycle (LC) models, our study analyzes the relationship between lifecycle CO2 (LC-CO2) emissions and the proportion of electric vehicle sales in Japan. We consider the contributions of fuel efficiency and vehicle lifetime to LC-CO2 emissions in three scenarios: changes in sales, improvement in fuel efficiency, and changes in vehicles’ lifetimes. Our findings show that promoting electric vehicles and decarbonization of electricity sector will decrease CO2 emissions from the driving phase. However, even if the energy mix follows the net zero emission target, emissions from the vehicle manufacturing phase will largely remain, and the manufacturing emissions from electric vehicle accounts for more than 50% of total emission in 2050 even in the case of the vehicle lifetime is extended by 5 years. Decarbonization of power sector is effective to reduce driving phase emissions, however it is insufficient for reducing LC-CO2 emissions. Thus, for reducing LC-CO2 emissions including the manufacturing phase, the Japanese government need to focus on the decarbonization of supply chain as well as reducing the driving phase emissions.