Karim Ansari Fard struck the winner in the 62nd minute as Team Melli fought hard to crack a tight North Korean defence. It put Iran on six points in Group D following their opening 2-1 victory over Iraq, ensuring them of a spot in the last eight with one match still to play - against United Arab Emirates on Wednesday.
Korea DPR's defeat followed their uninspiring scoreless draw with the UAE and leaves them staring at elimination from the tournament. UAE play Iraq later today in the other group game.
"The qualification of our team into the final eight for me is a fantastic accomplishment," Iran coach Afshin Ghotbi said. "Our group was a group of death and I still believe it is the most difficult group in the tournament. I'm very, very proud of my players and Iran," added the 46-year-old, in charge since early 2009. "Iran is capable of playing much better football and I think we'll show that in the coming matches."
It was a close encounter with Iran having to work hard to unlock the famously tight North Korean backline with few chances in a cagey start. Both sides had free-kicks from threatening positions in the opening ten minutes but neither made them count.
Bochum striker Jong Tae-Se had another chance on 16 minutes for Korea DPR but his free-kick was punched away by Iranian goalkeeper Mahdi Rahmati. Iran were struggling to break down North Korea's resolve but appeared to have opened the scoring in the 28th minute when Fard trapped a long ball in the box.
He beat defender Ri Jun-Il and slotted the ball past goalkeeper Ri Myong-Guk, but the linesman disallowed the goal and Fard instead got a yellow card for handball. The dangerous Japan-born Jong was a threat to Iran and charged their goal on the break soon after, trapping the ball in the box but his shot went meekly into Rahmati's hands.
Iran stepped up their offensive with a series of counter-attacks right after the interval. Mohammad Reza Khalatbari did well to collect a ball on the left but Myong was well placed to stop his shot in the 47th minute.
Jong, forming Korea DPR's frontline with captain and FC Rostov forward Hong Yong-Jo, invaded the Iranian area again on 51 minutes but two defenders bundled him out of the way before he could unleash a shot.
Khalatbari had another chance on the break near the hour mark but he found it hard to beat Myong. In the 62nd minute, Fard finally broke the deadlock as he volleyed a cross from the right on a lightening counter-attack and the ball caught Ri wrong-footed and zipped into the net.
Korea DPR fought back hard but missed a great chance 12 minutes from time when substitute Ryang Yong-Gi picked up a pass from Li Yun-Nam just outside the box but fell down as he tried to dribble past two Iran defenders.
Hong should have levelled the match in the closing seconds when he found himself with space in the penalty area and only the goalkeeper to beat, but the North Korean captain's shot grazed the top of the bar and flew harmlessly over.