The two teams were tied at 2-2 with just over a minute left to play. For a long time, it looked as though both teams were content with the situation, with neither side seeming particularly interested in pushing for a goal.
Austria may have been lulled into a false sense of security when Algeria star Riyad Mahrez unexpectedly broke through to make it 3-2 with just seconds left.
Iran then advanced as one of the best third-placed teams, at Austria's expense.
But it was to be even more dramatic. In the last second, Sasa Kalajdzic scored the equaliser for Austria, which took both teams through.
Algeria will face Switzerland in the round of 16. Austria will face Spain.
