Carrillo's error three minutes into the second half swung the tie in Urawa's favour despite Al-Hilal dominating for lengthy periods before the Japanese side added the crown to the titles they won in 2007 and 2017.
Urawa held the upper hand going into the second leg at Saitama Stadium after Shinzo Koroki's equaliser last Saturday had earned his team an away goal in the 1-1 draw in Riyadh.
The Saudis, missing the suspended Salem Al Dawsari and injured Salman Al Faraj, dominated the opening 45 minutes of the second leg, with Urawa's Alexander Scholz forced to clear Odion Igahlo's early effort off the line.
Goalkeeper Shusaku Nishikawa was called on to make saves to deny Brazilian winger Michael and Carrillo in a nervous opening for the hosts.
But it was Urawa who went closest to breaking the deadlock when Koroki's flying volley crashed against the crossbar as the striker emerged unmarked in the penalty area to meet Hiroki Sakai's inviting cross from the right.
Three minutes into the second half Urawa did go ahead, Carrillo putting into his own net after Marius Hoibraten's wind-assisted header across goal caused panic in the Al-Hilal defence to delight the majority in the 53,574 crowd.
Jose Kante and Kaito Yasui went close to scoring a second for the home side only for their efforts to sail wide of Abdullah Al Muaiouf's goal.
Al-Hilal, aiming for a record-extending fifth Asian crown, were denied the opportunity to take the game into extra-time in the 90th minute when Nishikawa reacted to push away Igahlo's goal-bound effort as Urawa held on.
