The left-handed opener, who served a 12-month suspension for his part in the sandpaper scandal against South Africa in March 2018, hit 107 off 111 balls as his side finished 307 all out.
Mohammad Amir’s 5-30 and Imam-ul-Haq’s assured half-century threatened to derail the defending champions’ bid to bounce back from Sunday’s defeat to India.
But Pakistan eventually fell short as their chase ended on 266 all out with 26 balls remaining, partly due to Pat Cummins’ 3-33.
Australia captain Aaron Finch, who also impressed with a knock of 82, had backed Warner to return to his “dangerous best” in the build up to the match.
Warner’s opening partnership of 146 with Finch was also the highest of the competition so far.
Their impressive alliance surpassed the 142-run stand between Bangladesh duo Shakib Al Hasan and Mushfiqur Rahim in the victory over South Africa.
Following a World Cup record three games rained off in five days, the International Cricket Council would have been relieved to see dry, albeit cold and cloudy, conditions in Somerset.
Pakistan were back in action for the first time since upsetting hosts England nine days ago after being frustrated by Friday’s washout.
They wore black armbands in respect of the recent deaths of former batsman Akhtar Sarfraz and Test umpire Riazuddin.
Amir began with a maiden after Pakistan won the toss and opted to bowl, before their momentum was stifled by the recalled Shaheen Afridi conceding 24 runs off two expensive overs with the new ball.
Finch, who bludgeoned six fours and four sixes during his hefty knock, benefited from slices of fortune as he survived a dropped catch from Asif Ali at slip, in addition to a strong lbw appeal which went to review.
He was eventually the first man out on the opening ball of the 23rd over after smashing Amir high and hard into the covers to leave Mohammad Hafeez with a straightforward catch.
Australia were still looking comfortable. However, after Warner was caught by Imam at deep point having sliced an Afridi delivery high into the air to leave the score 242 for four, the middle and lower order collapsed.
Reasons behind Pakistan's loss— Mazher Arshad (@MazherArshad) June 12, 2019
1) 4 specialist bowlers only
2) Three dropped catches
3) Bowled too short in first half
4) Over reliance on senior batsmen
Shadab as 5th bowler would have saved 20 runs or Haris as extra batsman would have scored 30-40 runs. #AusvPak
Spearheaded by the pace of Amir, Pakistan removed the final six wickets for just 30 runs in the space of only seven overs to give themselves a far more realistic target to chase.
Cummins ensured their response got off to a disheartening start as he removed Fakhar Zaman, caught by Kane Richardson at third man, for a duck at the start of the third over.
Babar Azam’s 30, Imam’s composed 53 and 46 from Hafeez steadied the ship slightly.
But the 1992 world champions lost a costly four wickets for 24 in 30 balls, beginning with opener Imam being caught down the leg side by wicketkeeper Alex Carey to become Cummins’ second victim.
Hasan Ali briefly entertained with 32 from only 15 balls before becoming Richardson’s second wicket. Australia had to be patient but eventually wrapped up a third win from four.
Mitchell Starc removed Wahab Riaz (45) and Amir, for a duck, in the space of three balls in the 45th over, before Glenn Maxwell ran out captain Sarfraz Ahmed (40) with a direct-hit.
Chris Gayle will “relish” the chance to take down England quicks Mark Wood and Jofra Archer, according to West Indies coach Corey Collymore.
Gayle is due to retire from one-day cricket after the World Cup and is eager to bow out on a high befitting his self-appointed “Universe Boss” moniker.
The 39-year-old proved there was plenty left in the tank when England toured the Caribbean over the winter, smashing a record 39 sixes in a drawn five-match series.
The teams reconvene at the Hampshire Bowl on Friday, when Gayle can expect to be faced with a barrage from Barbados-born Archer and Durham’s Wood.
Both men have hit 95mph since the start of the tournament, and Archer is a new addition to the England side, but very little worries the big-hitting Jamaican.
“Chris thrives on that. I have known him since he was 16 and he has always loved a challenge,” said Collymore, the Windies bowling coach.
“He has always enjoyed the challenge of fast bowling so I expect him to relish that. I have known Archer for a while and I saw Wood in the Caribbean last year.
“They are both very impressive, as we have seen throughout this tournament.”
Archer might well have raised the West Indian attack to a new level had they persuaded him to pursue an international future with them, but even in his absence they are no timid prospect.
In Oshane Thomas, Andre Russell, Sheldon Cottrell and Shannon Gabriel they have four seamers capable of making the batsmen hop, leaving Collymore to predict a fiery encounter.
“I did work with him (Archer) when he was a lot younger in Barbados. He was very impressive, the skills he shows now are ones we always had so we are expecting more of the same from him,” he said.
“But we have quick bowlers too so it should be a lively game.
“I don’t think many people like the short stuff, whether it is England or the West Indies. If you find a batsman that has a weakness to it, then you go after that.”
Provided by Press Association Sport
Assistant coach Sanjay Bangar confirmed that India will miss opener Shikhar Dhawan at least for the next three matches of the 2019 World Cup as India prepared to play New Zealand in Nottingham on Thursday.
Bangar said that India have not changed their preparations for the Kiwi clash even though they were thrashed by the Black Caps in the warm-up game.
“Look, every match is challenging, there are no easy matches here at this World Cup and in this format particularly,” Bangar said.
“That way nothing changes much for us, albeit the team we are facing is New Zealand or for that matter any other team. “