The victory saw England go unbeatable 2-0 in a three-game match.
England, with 158 points to win, finished 158-4 with seven balls to spare.
They needed 18 in the final two overs, and Australia failed to score 19 in two overs in a dramatic two-run loss in Game 1 on Friday.
But England got there with five balls from Adam Zampa, with Moeen Ali hitting a six and a four in successive deliveries of the leg-spinner.
Buttler finished the game with six in a row against Zampa.
This is how you win a game 💪A fantastic performance from the boys to seal the series! #ENGvAUS https://t.co/yyaQAHSdWB
– England Cricket (@englandcricket) 1599410526000
He faced just 54 balls, including Buttler’s highest scoring eight fours and two sixes this inning in a T20 international match, topping his 73 away against Sri Lanka in Southampton four years ago.
The victory was shaped by England’s attack, which held Australia to a modest 157-7 after the tourists won the draw.
Jofra archer they had caught David Warner for a third ball and Australia was 89-5 with seven overs remaining before a late play gave them a ray of hope.
England saw Jonny bairstow he handled Mitchell Starc for two fours before he fell to the left arm quickly in a strange way when, spinning around with a jerk, he knocked down the stumps with his bat and was out of hit for 19.
7️⃣7️⃣ * runs5️⃣4️⃣ balls8️⃣ fours2️⃣ sixes3️⃣ catches What a performance from Man of the Match, Jos Buttler… https://t.co/JgZ8LWVXNb
– ICC (@ICC) 1599412057000
But Buttler drove the pacemaker Kane Richardson for six and the Dawid malan matched two fours of successive deliveries of spinner Glenn Maxwell.
And when Ashton Agar’s left arm spinner came on, Buttler deftly swept it in reverse for four.
Pat cummins he was called to attack, but left-hander Malan carried him over extra coverage for an excellent four before Buttler pushed him to another limit.
An 87 save ended when Malan holed 42 from Agar, but Buttler continued to manipulate the field.
England, who have battled for Powerplay wickets, got off to a sensational start after missing the pitch when speedy pitcher Archer had the dangerous Warner trapped behind for nothing.
Warner immediately checked, but replays confirmed that he had put the ball on with gloves and Australia was nothing to one.
Australia was 3-2 in the second round, after left-hander Alex Carey, promoted to number three in place of star hitter Steve Smith, gave himself room to drive, but only outscored Mark Wood, like Archer in a World Cup. From 50 onwards he quickly beat a bowler, to goalie Buttler.
Archer, topping speeds of 91 mph, was pulled from the attack after a wicket spell for eight runs in two overs.
Smith, at number four, took out Tom Curran for six.
But Smith ran out of ten for the captain of England Eoin MorganDirect blow from the armpit from the middle of the field with a single stump to aim.
The series concludes in Southampton on Tuesday.
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