The reigning K-League champions were frustrated in the early stages of the game at the Seoul World Cup Stadium last Wednesday.
But Montenegrin forward Dejan Damjanovic finally broke the Iranian outfit's stubborn resistance in the 39th minute. And Seoul put one foot in the final shortly after half-time when Yo-Han Ko doubled their advantage.
Damjanovic has been highly influential in the side's run in the 2013 Champions League and scored in both legs of the club's 2-1 aggregate victory over Al Ahli in the quarter-final.
The 32-year-old will once again lead the line in attack and could be pivotal if the team are to hold out to reach the final for only the second time, the club's first appearance coming in 2001-02 as the Anyang Cheetahs.
The 2-0 win in the first leg has left Choi Yong-soo's side in a strong position to challenge for their first Champions League title, and it would mark the first time they have made the final in its current guise.
Iranian champions Esteghlal are looking to win the tournament for the first time since the format was revised for the 2002-2003 season - they won twice in previous formats - but face an uphill battle to reverse the tie at the Azadi Stadium.
Esteghlal have been blighted by a series of inconsistent performances this season, having won five and lost three of their nine matches in the Persian Gulf Cup.
They are currently 10 points adrift of leaders Foolad, although they do have two games in hand over all the sides above them in the league.
Strikers Farhad Majidi and Arash Borhani drew blanks in the first leg, but - having netted three goals apiece in the competition thus far - will be vital in attempting to reverse Esteghlal's fortunes.
