Head, playing his first ODI since 2018, cracked 101 off 72 balls on Tuesday to help set the platform in the first of the three-match series.
Ben McDermott added 55 off 70 balls as Australia raced to 1-171 in the 25th over, but the run rate then slowed due to the regular fall of wickets.
Only some late lusty blows from Cameron Green (40no off 30 balls) ensured Australia picked up the pace again.
Head was on just one when he was given out lbw in the second over.
The 28-year-old immediately reviewed the decision, with replays showing Mohammad Wasim's delivery had pitched outside leg stump.
Head made the most of the reprieve, punishing anything wide to bring up his half-century off 32 balls.
By the time Head brought up his ton off 70 balls, he had cracked three sixes and 12 fours.
It was the fastest ODI century by an Australian against Pakistan.
But his innings came to a meek end when he chipped Iftikhar Ahmed to mid-off soon after bringing up triple figures.
McDermott would have been given out on 20 had Pakistan reviewed an lbw shout that was turned down.
The 27-year-old brought up a hard-fought half-century, but was run out shortly after when he set off for a doomed third run and was sent back by Marnus Labuschagne.
Labuschagne (25), Aaron Finch (23), and Marcus Stoinis (26) all made starts, but none were able to go on with the job.
Paceman Haris Rauf was the pick of the Pakistan bowlers with figures of 2-44 off eight overs, while 34-year-old spinner Zahid Mahmood snared 2-59 on debut.
Australia entered the match with just 13 fit players to choose from after being ravaged by injuries and COVID-19.
Less than 24 hours after Josh Inglis entered isolation after contracting COVID-19, spinner Ashton Agar was also struck down with the virus.
Allrounder Mitch Marsh was ruled out of the series-opener with a hip injury, while Steve Smith left after the Test series due to an elbow complaint.
Agar's withdrawal paved the way for Mitchell Swepson to make his ODI debut.
Paceman Nathan Ellis, 27, was also handed a debut in the absence of Mitchell Starc, Pat Cummins and Josh Hazlewood, who have all been rested for the white-ball part of the tour.
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