Oman looked set to frustrate the Socceroos team of European stars before the Everton midfielder rifled home the winner 16 minutes from time. It was Cahill's 19th goal in 36 internationals.
The hard-earned victory hoisted Australia to the top of Group B with a crucial three points after their scratchy start to qualifying for the 2011 tournament in Qatar. The Aussies had put themselves in trouble when a below-strength side was upset 1-0 by Kuwait in Canberra in March after drawing 0-0 with Indonesia in Jakarta last January.
"I think we should have scored more goals," Australian coach Pim Verbeek said. "In the first 10-15 minutes we should have scored at least one and then we started playing out of our organisation, we were too attacking, but in the second half we did much better with our formation."
Oman looked on course to repeat their determined performance from the 2007 Asian Cup in Bangkok, when the Australians needed an injury-time goal from Cahill to scrape home with a 1-1 draw. However, Australia's repeated attacks finally were rewarded by Cahill's strike.
Oman weathered an early Socceroo onslaught and matched their more illustrious rivals for the rest of the opening 45 minutes. A Cahill header skimmed the bar and Josh Kennedy had a shot saved before the Omanis worked their way back into the contest.
Midfielder Fawzi Bashir gave the Aussies a big fright in the 23rd minute when goalkeeper Mark Schwarzer pushed his fizzing volley on to an upright, before Amad Al Hosni blasted over the bar after being put through by Bashir minutes later. Kennedy then had a header well saved by goalkeeper Ali Al Habsi before midfielder Jason Culina let fly with a rasping long-range volley that was just wide in first-half stoppage time.
Al Habsi had the good fortune of saving Lucas Neill's shot with his head just after the resumption as Oman rode their luck. Cahill finally broke the deadlock in the 74th minute after Scott Chipperfield broke free on the left. His pass was flicked on by Kennedy into the path of Cahill, whose volley went in off the far post to the relief of the 20,595 home crowd.
Oman's veteran French coach Claude Le Roy said Australia did not deserve to beat his team. "I am very disappointed because we know we aren't the best team in the world, but this team has a fantastic spirit, it's very loyal and but maybe sometimes a little naive," Le Roy said. "We'll be ready for Australia when they come to Muscat next month."
Oman host the return leg against the Socceroos in Muscat on 14 November.