Midfielder Mohamed Al-Shalhoub scored the match's only goal with a brilliant left-footer to give Hilal the win.
The result put the Riyadh powerhouse in second spot in the league table on 44 points and earned them a place in the semi-finals, as the Saudi league adopts a knockout system in its final phase.
Despite the defeat, Shabab remain atop the league summit on 45 points and will qualify automatically to the final match.
Elsewhere, Ittihad Jeddah produced a 3-0 drubbing of Abha to finish in third place with 42 points.
Sierra Leone international Mohamed Kallon scored a brace for the Asian champions while Saad Al-Aboud added a third.
Ittihad will now take on arch-rivals Ahli in the first semi-final after the latter crushed Al-Ansar 4-0 to finish in 4th place on 36 points.
Abdelhak Ait El Arif and Walid Al-Jizani scored a double each to hand Ahli the win.
In the final phase of the Saudi league, Ittihad will host Ahli and the winner will travel to Riyadh to face Hilal and the winner from that game will face Shabab in the final.
Abha and Al-Ansar were relegated to the second division after finishing in 11th and 12th places respectively.