Both goals at King Fahd International Stadium came in the first half.
Rafael Silva gave Urawa the early lead and an away goal, while Omar Khribin equalized with his 10th of the tournament.
Urawa, the one-time champion a decade ago, was on the board after just eight minutes through Silva’s low shot from inside the area.
The Saudi side responded with pressure on Urawa goalkeeper Shusaka Nishikawa, who had to make several saves, especially from Khribin.
The Syrian striker, in the running for the Asian Football Confederation player of the year award, made amends eight minutes before the break, shooting past Nishikawa from close range.
The second leg is next Saturday at Urawa’s Saitama Stadium.