It was Dumoulin’s second successive runner-up place on a Grand Tour after he failed to defend his 2017 Giro d’Italia crown last May when Chris Froome beat the Dutchman to the pink jersey.
Dumoulin, who rides for the Sunweb team, finished his campaign on a high after winning the penultimate stage time trial.
“I’m genuinely happy with my second place,” Dumoulin said when asked if he felt frustrated at finishing second. If someone told me, after such a hard Giro, that I’d win a stage at the Tour and finish second, I’d have signed.
“I’m happy for Geraint. He was never put into trouble by anyone in the mountains, or on any stage, also not by me. I only have respect for him. Congratulations from me.”
Thomas succeeds four-time winner and Sky teammate Froome, who finished third, to become the third British winner of the race since Bradley Wiggins made history in 2012.
Froome won his maiden Tour a year later and, after Vincenzo Nibali’s 2014 victory, the Kenyan-born Briton won from 2015-2017.
After seeing his bid for a record-equalling fifth win hampered by crashes and a lack of form in the mountains, there was speculation Froome could actually challenge Thomas in the Pyrenees.
“It’s clear both of them have a lot of ambition,” Spanish rival Mikel Landa, of Movistar, suggested a day before the race moved into the Pyrenees.
“Sooner or later, the ego and ambition of each of them will show.”
But, when pushed into helping Thomas keep the yellow jersey in Sky hands after years of benefiting from the Welshman’s help, Froome obliged on the bike — and when it came to handing out the plaudits afterward.
“He’s been a massive part of my Tour victories. If he was going to be on the podium, he was going to be on the top step,” said Froome.
“To be on the podium alongside Geraint is a dream.”
Thomas’s victory means Sky have won six of the past seven editions of the race.
Although it has given Sky chief Dave Brailsford a likely selection headache for next year, he was full of praise for Thomas.
“He’s very loyal. There’s never any doubts with him,” said Brailsford.
“Now he’s being repaid for all the years of hard work and sacrifice he made for the team. The guys are happy, so happy to work for him.”
“I didn’t think I’d win the Tour,” said Thomas after he finished 14-seconds behind Dumoulin on Saturday.
“That was the most I’d ever suffered, day in, day out.”
Dumoulin may or may not be back for another tilt at the yellow jersey next year.
“It depends on the race route,” he said.
But he has no doubts about who deserved to be in yellow this time.
“I have no regrets at all. Thomas was the absolute strongest over the three weeks, and he showed that every day.”