Herve Renard's side only needed a point against Graham Arnold's Iraq, and an injury-time save by goalkeeper Nawaf Al-Aqidi to keep out Hassan Abdulkareem's curling free kick ensured the Saudis confirmed their progress.
The result means Saudi Arabia win Group B of the fourth round of Asia's preliminaries, finishing level on four points with the Iraqis but ahead of their neighbours on goals scored after recording a 3-2 win over third-place finishers Indonesia.
Both sides struggled throughout a tense opening 45 minutes played in front of more than 60,000 fans, with Saleh Abu Al-Shamat posing the greatest threat to the Iraqi defence as he shot over the bar in the 13th minute.
The Al-Ahli forward unlocked the visitors' defence soon after the restart when he played a perfectly weighted pass into the path of Feras Al-Brikan, the striker fizzing a ball across the face of goal from which Saud Abdulhamid shot wide.
Al-Shamat continued to cause problems for the visitors, but Jalal Hassan threw himself to his left to keep out a goal-bound strike six minutes after the restart.
Hassan then denied Saudi captain Salem Al-Dawsari as the opportunities increased in regularity, with Nasser Al-Dawsari also frustrated by the Iraqi goalkeeper in the 63rd minute.
A last-ditch tackle by Hassan Al-Tambkti stopped Iraqi forward Mohanad Ali on a rare sortie forward 15 minutes from time, while Abdulkareem went closest of all for his team deep into injury time.
However, his curling left-foot free kick from 25 yards out was pushed to safety by Al-Aqidi when he dived to his right, and the Saudis prevailed to qualify for a seventh World Cup since making their debut in 1994.
