Fresh from setting a new world record of 6.31m in Uppsala earlier this month, Duplantis was returning to the city where he set his first world record six years ago. He began the competition using the height of 5.50m as something of a warm-up, before clearing 5.85m just as easily.
The Swede then opted to skip 5.95m, a height that his expected nearest challenger, Emmanouil Karalis of Greece, managed to clear. So did Sondre Guttormsen of Norway, while Kurtis Marshall of Australia failed once at 5.95m but opted to attempt 6.00m.
With the field whittled down to four, Mondo then made light work of his first attempt at 6.00m - his 126th clearance of 6.00m or higher - while Marshall managed to set a new personal best.
The Louisiana-born Swede kept the game of cat-and-mouse alive by skipping 6.05m, which Karalis cleared to guarantee silver, while Guttormsen's attempts at 6.05m having not cleared 6.00m failing ensured bronze for Marshall, ahead of the Norwegian.
Duplantis then cleared 6.10m, before Karalis decided to go straight for 6.20m, which he failed. The mind games continued with Duplantis attempting 6.25m, which he again cleared at the first time of asking to set a new championship record, but gave the bar a huge wobble in the process.
Karalis had two attempts at 6.25m but couldn't match the superstar Swede, which took his failures to three in a row, giving Mondo yet another major gold medal.
The crowd were anticipating a try at 6.32m, but Mondo packed away his poles and didn't have a go at the world record on this occasion.
Also in the evening session, Vera Sjoberg finished seventh in the women's 3000m on her first major championships over that distance, crossing the line in a time of 9:03.57.
Sitting in the second half of the 15-racer bunch in the earlier laps, Sjoberg had drifted to become the back marker midway through the race, a blessing in disguise as contact further forward saw Ethiopia's Freweyni Hailu take a fall.
In the latter stages, the 24-year-old former 1500m runner began to pick off the tiring runners ahead of her, making her way through the field, eventually pipping Spain's Marta Garcia to finish seventh.
The Swede was too far back to contest the medals, with the gold won by Italy's Nadia Battocletti, ahead of Emily Mackay of the United States, who beat Australia's Jessica Hull to silver.
