Brazil winger Galeno broke Kawasaki's resistance in the 35th minute on Saturday when he bent an unstoppable strike into the top corner to send the home side on their way to a first Asian title, with Franck Kessie heading in their second seven minutes later.
The victory makes Al-Ahli the third Saudi club to win the competition in its various guises, joining city rivals and twice winners Al-Ittihad and Riyadh's four-times champions Al-Hilal.
"We are so proud," said Al-Ahli goalkeeper Edouard Mendy. "Once we knew the final eight would be played in Jeddah it was our goal to be champions in front of our fans. Since I came here 18 months ago, they have supported us so much.
"As I said when I signed here, it's to make history, to continue to win trophies and make this club as big as it was before."
Al-Ahli were heavy favourites with a line-up featuring an expensively acquired array of foreign talent that included UEFA Champions League winners Riyad Mahrez and Roberto Firmino, who once both starred in England's Premier League.
Twice inside the opening six minutes Louis Yamaguchi denied the home side, the Kawasaki goalkeeper blocking Ivan Toney's viciously struck right-foot effort before making a point-blank block at the resulting corner from Ziyad Al-Johani.
The Japanese outfit almost silenced the crowd in the 11th minute with a moment of individual skill from Marcinho, the Brazilian gliding beyond Ali Majrashi to bear down on goal only to shoot across the area and past the far post.
Toney fired wide and Roger Ibanez was just off target with a curling effort from the edge of the area as Al-Ahli increased the pressure, but a disciplined Kawasaki held firm.
However, the opener eventually came with 10 minutes remaining of the first half when Kawasaki gave away possession close to their own goal.
Firmino fed Galeno in space 25 metres out and, as midfielder So Kawahara made a late, vain attempt to close the Brazilian down, the former Porto man bent a perfectly-measured right-foot strike into the top corner.
Al-Ahli doubled their lead soon after, the Saudi side capitalising on their opponents being temporarily down to 10 men with left back Sota Miura off the field injured.
Firmino was heavily involved again, bursting through on the right side of the area to clip a cross into the six-yard box that the quickly arriving Ivorian Kessie rose to head home.
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