"I'm sorry it wasn't pretty, but we beat them ... Let's look at the positives tonight - we're going to Brazil," said captain Lucas Neill.
Iran, South Korea and Australia now join Japan, the Asian Cup-holders who booked their ticket a fortnight ago, at next year's World Cup as the only countries to have qualified alongside hosts Brazil.
Although all four Asian qualifiers are familiar names at the World Cup, the year-long elimination process has been hard-fought and came down to the last week of the final group stage.
Tensions were high yesterday and especially in Ulsan, where South Korea had promised to "make life painful" for Iran and to draw "tears of blood" from their captain, Javad Nekounam.
Ex-Middlesbrough striker Lee Dong-Gook tested Rahman Ahmadi with a stinging attempt from distance but despite dominating the first half, South Korea struggled to create clear chances.
Iran started the second period with more ambition and on 59 minutes, they were suddenly in front thanks to a defensive howler from Kim Young-Gwon and the alert thinking of Reza Ghoochannejhad.
- AAP