Symonds, dropped twice on 24 and 82, faced just 103 balls with one six and nine fours on Saturday.
It was the all-rounder's second One-day International century, his first a blistering 143 not out against Pakistan at the World Cup last year.
Australia were 148 for five off 34 overs when Symonds and Michael Clarke, who made a run-a-ball 31, came together and put on 88 to revive the innings.
Symonds led an onslaught that saw 50 runs come off the last five overs.
He was particularly severe on Shoaib Akhtar, the 'Rawalpindi Express' seeing his eight overs cost 70 runs.
Fellow quick Mohammad Sami took two for 56 in an innings where opener Matthew Hayden's 52 was the only other major score.
Pakistan, looking to avenge their 17-run defeat by world champions Australia in last week's Dutch triangular final in Amstelveen, made early inroads after captain Inzamam-ul-Haq won the toss.
Sami, with the ground bathed in sunshine, struck twice in a spell of two wickets for three runs in 10 balls to leave Australia 30 for two.
First he had wicketkeeper Brad Haddin (13) failing to get over the top of a steepling delivery on the backfoot and lobbing a catch to Shoaib Malik at short cover.
Sami then pinned Ricky Ponting lbw for just four after the Australia captain shuffled across his stumps.
Hayden looked out of touch early on but pressed on to a 78-ball fifty with six fours.
But on the left-hander, playing forward to leg-spinner Shahid Afridi's fourth ball, got a faint inside edge and was bowled to leave Australia 99 for three in the 21st over.
And 10 runs later Damien Martyn (26) dragged a drive against off-spinner Malik to Imran Farhat at short mid-on.
Martyn's exit brought in Symonds for what turned out to be a second rescue mission against Pakistan. At Johannesburg last year Australia were 86 for four when Symonds came to the crease and unleashed his whirlwind century.
But he should have been out when Rana Naveed, sliding in on his knees from long-on, failed to hold a catch off Malik.
But four balls later the bowler ran out Darren Lehmann (nine), backing-up, when after fielding a Symonds drive his back-flick throw hit the stumps.
Clarke went when his skied hook off Akhtar was well caught at mid-on by Malik before Symonds's cut to third man off the same bowler was dropped by Yousuf Youhana.
Symonds then hooked the first ball off the last over, from Akhtar, for six and two balls later stepped outside his leg-stump to hit a four to go to 99 before a two took him to his hundred.
In 1999 Australia beat Pakistan at Lord's by eight wickets to win the World Cup final and when the teams met at the ground two years later, Australia enjoyed a nine-wicket win in the NatWest triangular final.