The Syrians, competing at the 16-team finals for the first time in 15 years, fully deserved the victory with players and substitutes sprinting over to their delighted supporters at the Al Rayyan Stadium to celebrate and pray.
The win was their first over the Saudis since 1976 and only their second in 24 attempts.
Syria, ranked 107th by FIFA and 26 places below their opponents, defended tightly and caused the three-times Asian champions numerous problems down the flanks with striker Mohamad Al Zino looking dangerous throughout.
"This is a battle and we have not yet won the war. The difficult part is just starting," said Tita Valeriu, who last month was appointed the team's fourth coach in a year.
Roared on by passionate support, the Syrians took the lead seven minutes before halftime when Al Husein prodded a half-volley from the edge of the area towards goal.
The shot was then diverted past Saudi goalkeeper Waleed Abdullah by his full-back Abdullah Shuhail's slight headed touch.
The Saudis improved after the break and drew level in the 59th minute when substitute Taiseer Al Jassam leapt into the penalty area to head Mosab Balhous's punched clearance from a corner back past the Syrian goalkeeper.
The equaliser momentarily silenced the Syrian supporters, who made up most of the 15,768 crowd at the 22,000 all-seater stadium.
They were back cheering again just four minutes later, however, when Al Husein's right footed shot from just inside the area took a wicked deflection past Abdullah to restore the advantage.
"I like very much the fans and spectators, they were like the 12th player in the game," Valeriu told reporters.
The Syrians survived some nervy moments in the last 10 minutes as they sunk deeper into their half with substitute Naif Hazazi going very close with a header in the final minute.
The defeat left Saudi Arabia's Portuguese coach Jose Peseiro under more pressure after he was criticised for their failure to qualify for the World Cup for the first time since 1990 last year, despite joining midway through the qualifying campaign.
"We lost the first game but I believe we can win other games. Spain lost the first game in the (2010) World Cup and won the World Cup," said Peseiro.
The result came after three-times Asian champions Japan grabbed a stoppage-time equaliser to draw 1-1 with Jordan in the other Group B match.
