The Saudi Arabian outfit were beaten comprehensively by South Korean team Ulsan in last year's final and will be determined to go one better this year.
Vitor Pereira's side breezed through the group stages without losing a game and dropped just four points, before following that up by overcoming El Jaish 3-1 on aggregate in their round of 16 encounter.
But they face a difficult task against South Korean champions Seoul, who ousted Chinese outfit Beijing Guoan 3-1 over two legs in the previous round.
Al Ahli will be looking to make home advantage count in the first leg when the sides meet at the King Abdul Aziz Stadium on Wednesday.
The winner of that tie will face the victor of the quarter-final match between Iran outfit Esteghlal and Thai side Buriram United in the semi-final.
Esteghlal booked their place in the last eight with a 4-2 aggregate victory over Dubai outfit Al Shabab, while Buriram ensured their progress with a narrow 2-1 over Bunyodkor.
Guangzhou Evergrande will look to take their mightily impressive league form into their last-eight showdown with Qatar outfit Lekhwiya.
Evergrande are currently unbeaten in the Chinese Super League, and will be confident of progression after a 5-1 drubbing of Australian side Central Coast Mariners in the round of 16.
Marcello Lippi's side are gunning to be the first winners from China since the competition took on its current Champions League guise in 2002.
Liaoning FC were the last team from China to win the competition in its previous guise the Asian Club Championship.
Japanese side Kashiwa Reysol and Saudi Arabia's Al Shabab will battle to face Evergrande or Lekhwiya.
Reysol are enduring a disappointing campaign in the J.League and currently sit in 11th spot.
But their Champions League form has provided some comfort and they were particularly impressive in the round of 16, with a 5-2 aggregate win over Jeonbuk Motors.
