The pair beat Kveta Peschke of the Czech Republic and Aisam-ul-Haq Qureshi of Pakistan 6-4, 6-4.
Bryan and Qureshi will face each other again Friday in the men's doubles final, two competitors with much mutual respect. The American said during Thursday's trophy ceremony that his charitable foundation, which he runs with doubles partner and twin brother Mike, was donating money to Pakistani flood relief.
"Those guys are great guys," Bryan said of Qureshi and teammate Rohan Bopanna of India. "Everyone in the locker room likes them. Just hearing about the problem, talked about it with my brother and my dad and just wanted to do it."
The floods began in northwest Pakistan at the end of July after extremely heavy monsoon rains and slowly surged south along the Indus River, swallowing up hundreds of villages and towns and killing more than 1,700 people. Another 17 million have been affected by the floods, and many will need emergency assistance to survive.
"Every little bit helps," Qureshi said. "I've been trying to send some good news back home from here for two weeks. ... It's a really, really kind gesture. I owe them."
Told he could pay the Bryans back by giving them the men's doubles title, Qureshi joked, "I gave him the mixed doubles title today."
Win or lose Friday, it's been a highly successful tournament for Qureshi. He reached the two finals -- unseeded in mixed doubles, seeded 16th in men's.
"I've spent the last 14 years trying to put tennis in the spotlight in my country," the 30-year-old Qureshi said. "Cricket's like a religion there. This moment is like a highlight in my career. When I was growing up, I thought maybe someday I could win a Grand Slam or make it to one Grand Slam final. But two Grand Slam finals in a week? It's unbelievable."
And now Peschke is by far the most popular Czech in Pakistan.
"Every time there's a report about me, her picture is up there with me," he said. "People have been coming up to me asking how to pronounce her name, because they pronounce it differently on every TV show.
"To be honest," he added, "I don't know how to pronounce it, either."
For the record, it's KVE-tuh PESH-keh.
Huber and Bryan also won last year's French Open. Huber, who was born in South Africa, became an American citizen in 2007.
Huber and Russia's Nadia Petrova, seeded second, are in the women's doubles semifinals.
The Bryan brothers are famous for their high-flying chest-bumping celebrations. That doesn't translate well to mixed doubles.
"He wants to chest bump, chest bump, chest bump," Huber said with a laugh. "I'm like, no. Do it with your girlfriend; don't chest bump me."