Brenner finished the seven-stage, 1,100-kilometre race 10 seconds ahead of New Zealand's Finn Fisher-Black and 16 seconds ahead of Spain's Ivan Romeo.
Küng won the 12.5-kilometre time trial in the southern town of Wieliczka in 15 minutes and 10 seconds, finishing 4 seconds ahead of Fisher-Black and Britain's Callum Thornley. Brenner was 11 seconds behind Küng.
Küng cried with joy after crossing the finish line. In his first interview, he said he had feared his career was over after breaking his femur in February.
Poland's Michał Kwiatkowski was the country's best finisher in the time trial, placing 31st, 36 seconds behind Küng.
Filip Gruszczyński of the Polish national team was the highest-placed Polish rider overall, finishing 25th, 2 minutes and 48 seconds behind Brenner.
Polish President Karol Nawrocki presented Brenner with the winner's trophy.
The race has been held under the auspices of Poland's head of state since its first edition in 1928, but Nawrocki was the first sitting president to attend the awards ceremony in person.
Poland's President Karol Nawrocki (third from left) attends the Tour de Pologne awards ceremony on Sunday, Aug. 9, 2026. Photo: PAP/Art Service
Nawrocki thanked race director Czesław Lang for organising the event, which he said promotes Poland, as well as the fans who supported the riders during the seven days of competition.
This year's race crossed Poland from north to south, starting in Gdynia on the Baltic coast and ending in Wieliczka near the historic city of Kraków.
Italy's Jonathan Milan won each of the first three sprint stages, finishing fastest from the main group in Koszalin, Szczecin and Zielona Góra.
The climbers took centre stage from the fourth stage, with Dutchman Bart Lemmen earning the first professional victory of his career in Karpacz and France's Louis Barre winning in Bukowina Tatrzańska.
Switzerland's Jan Christen won at Mount Kocierz in the Beskid Mały range for his first World Tour victory.
After six stages, the overall standings were tightly packed. Italy's Christian Scaroni led Barre by three seconds and Lemmen by five, but none of the three was considered a time-trial specialist, and they lost ground in Sunday's decisive stage.
Brenner had started the final stage in fourth place, 11 seconds behind Scaroni.
The 23-year-old German had few major results before this year's Tour de Pologne. He consistently finished near the front on the mountain stages, placing fourth in Karpacz, second at Mount Kocierz and third in Bukowina Tatrzańska.
Marco Brenner in action at the 2026 Tour de Pologne. PAP/Grzegorz Momot
He made up the deficit in the time trial and held off his rivals to secure the overall victory.
Gruszczyński, 21, was a pleasant surprise for Polish fans. The young rider, who is still developing at the elite level, performed strongly in the mountains and finished 25th overall on his Tour de Pologne debut.
Kwiatkowski, the 2018 Tour de Pologne winner and a former world champion, had a disappointing race, finishing 40th overall, nearly 10 minutes behind Brenner.
Poland's Radosław Frątczak of the national team was named the race's most active rider.
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Source: IAR, PAP, TVP Sport