Fernando Verdasco and Anabel Medina Garrigues beat the more fancied pairing of Novak Djokovic and Ana Ivanovic 6-4 7-5 in the deciding mixed doubles to secure a 2-1 win.
World No.1 Djokovic had already defeated Verdasco 6-3 7-5 in the opening singles before Medina Garrigues survived a tense clash against Ivanovic, 6-4 6-7 6-2.
"Thanks to Fernando because without him, the doubles would have been impossible," Medina Garrigues said.
Verdasco led Djokovic 3-0 in the second set of their singles rubber before being overhauled. "It's difficult to play against a player like him," Djokovic said. "He's very aggressive and serves over 200kmh."
Djokovic is chasing his third successive Australian Open at Melbourne Park from January 14.
He suffered a shock loss to Australia's Bernard Tomic during the round robin stage of the Hopman Cup but recovered with back-to-back singles wins against Andreas Seppi and Verdasco.