Captain Kwak Tae-hwi opened the scoring in the 13th minute with Brazilian forward Rafinha (68th) and midfielder Kim Seung-yong (75th) adding second half goals as the Koreans dominated the final they hosted in Ulsan after a draw by organisers.
The 3-0 win was Ulsan's ninth consecutive victory in Asia's premier club tournament, which they went through unbeaten, as a South Korean team lifted the trophy for the third time in four years.
Ulsan collected the trophy from AFC acting president Zhang Jilong and will now represent Asia in the Club World Cup next month in Japan where they will take on Mexican side Monterrey in the quarter-finals.
The victory in the south-eastern city never looked in doubt once Ulsan took the lead thanks to their big central defender Kwak Tae-hwi, who glanced a header from Kim Seung-yong's free-kick in to corner of the Al Ahli goal.
Ulsan strikers Rafinha and Kim Shin-wook caused the visitors numerous problems as the home side played in a surprisingly direct style in contrast to the more possession-conscious play that had helped them reach the final for the first time.
But while the Koreans routinely pinned Al Ahli back in their own half with a pressing high defensive line, they struggled to test the Saudis goalkeeper Abdullah Mayyof.
The visitors' best chance came in the 40th minute when Moataz Al-Musa expertly controlled a ball into the box but his strong right foot shot was well blocked before his team mate Victor saw his rebound cleared by a scrambling Ulsan defence.
Brazilian Victor had a couple of further half chances after the break before Kwak missed a great chance to double the advantage on the hour mark, but he wasted a free header after another pinpoint free-kick from deep by Kim Seung-yong.
Ulsan did grab a second seven minutes later when another long ball into the box was headed across goal by the towering Kim Shin-wook and Rafinha was on hand to bundle the ball in from close range, celebrating with a 'Gangnam style' dance.
Al Ahli, playing their first match outside of the Middle East in this year's tournament, looked beaten and their heads dropped as Kim Seung-yong added some shine to the victory with a third seven minutes later.
The dead-ball specialist neatly controlled a cross to the back post on his chest before rifling home a powerful right foot shot to the joy of the home crowd.
Kim Shin-wook twice came close to adding a fourth in the dying stages as Al Ahli lost their discipline playing in the cool temperatures in Korea.