Passing the opening two heights, Duplantis sailed over 5.60m at the first attempt when he entered the competition, and with only 11 others able to match that height, that was all the Swedish superstar needed to qualify for the final, which takes place on the final evening of competition on Sunday 16th.
Mondo looked fresh and comfortable following the injury he suffered in London earlier this season, but with only one attempt some 80cm shorter than his latest world record, only on Sunday will fans see if he is back to his best.
His closest challenger in recent years, Emmanouil Karalis of Greece, was also "one and done" at the 5.60m height.
Duplantis' compatriot William Asker will not be joining him in the final. The 22-year-old cleared 5.45m but only at the second attempt, a miss that saw him miss out on one of the final three spots up for grabs.
Confident starts from Pihlstrom and Karlsson
Samuel Pihlstrom took control of his 1500m heat, getting himself to the front with just over 300m gone and controlling the increasing tempo. With 200m to go, he was passed by Great Britain's Jake Wightman and Germany's Robert Farken, but the Swede still had enough to hold off further challengers in the home straight to finish third in 3:41.84 and qualify for the final, taking place in the evening session on 15th August.
Lovisa Karlsson began two days of events in the heptathlon with one of her strongest events, the 100m hurdles. In the heat for faster athletes, she was second at the halfway mark before being pipped on the line to finish fourth in 13.03, which also put her fourth overall. Down in 19th after the hurdles was Erika Warff, who ran 13.83 in the opening event. Next up was the high jump, in which Warff registered 1.74m, 3cm higher than Karlsson, but with the best jumpers clearing 1.86m, Karlsson was knocked down to 11th overall on 1987 points, while Warff climbed two places to 17th on 1906 points.
Meanwhile, there will be no women's javelin final for Beatrice Lantz, whose furthest throw of 51.06m saw her finish 29th in the 30-athlete field.
Top qualifiers go for medals in evening session
In the evening session, Oskar Edlund will be aiming to replicate the national record of 47.81 he set to finish quickest in the semi-finals of the 400m hurdles, as he competes for the medals in the final.
Vanessa Kamga also comes into the women's discus final having set the best mark in the previous round, while Caisa-Marie Lindfors is also looking to compete for medals having qualified in 10th.