It was the first time Iran had beaten Qatar in four qualifying matches for Brazil 2014. Their three previous matches, including two in the third and penultimate phase of qualifying, had ended in draws.
Tuesday's victory took Iran to ten points in Group A, and with two more games in hand, the Asian giants look set for their fourth appearance in the FIFA World Cup finals.
Qatar's already slim hopes of qualifying for football's showpiece event relied heavily on a victory over Iran, and for the better part of the first half they appeared on course with speedy moves that occasionally caught the Iranians napping.
Former AFC Asian Player of the Year Khalfan Ibrahim came close to beating the Iranian defence on a couple of occasions, but Qatar's first real chance came in the 30th minute when Hassan Haydos found himself clear just inside the penalty area. However, much to Qatar's dismay his cracking shot slammed the crossbar.
Qatar goalkeeper Qassem Burhan then brought off two splendid saves in quick succession - blocking a dipping free-kick from 25 yards by Masoud Shojaei and then producing a reflex save to stop a Nournia header from close range.
Iran, however, moved up a gear in the second-half. Playing with more purpose and speed they kept probing at the Qatari defence and eventually it cracked under pressure when a move initiated by Qatar-based Andranik Teymourian saw the ball come Nournia's way and the former Dutch U-19 international made no mistake from close range. Qatar tried their best to get the equaliser but the Iranians held firm to deny the hosts