Allahyar Sayyadmanesh opened the scoring after 29 minutes before Mohammad Ghaderi doubled its advantage early in the second half and Alireza Asadabadi gave Vietnam a mountain to climb just after the hour.
A dominant Iran then put its opponent to the sword as Amir Khodamoradi and Sayyadmanesh’s double wrapped up a comfortable win as Abbas Chamanian’s side progressed to the last four and also ensured a return to India for the 2017 FIFA U-17 World Cup as one of the tournament’s top four teams.
Iran has been scheduled to face winner of Oman and North Korea on Thursday.