Lopez-Verdasco beat Tomas Berdych and Radek Stepanek 7-6 (9-7), 7-5, 6-2, giving Spain an insurmountable 3-0 advantage in the best-of-five event in Barcelona, Spain.
It was Spain's fourth Davis Cup title in the last 10 years.
The victory started Friday when former World No. 1 Rafael Nadal and former Top 10 star David Ferrer won their singles matches over Berdych and Stepanek.
"We didn't expect to win it this quickly," said Spain's captain, Albert Costa. "The key to this team has been its unity."
"It's unbelievable to win the Davis Cup two years in a row," added Verdasco.
Before Saturday's loss, the 6-foot-5 Berdych and Stepanek had not been beaten at a Davis Cup doubles doubles match in five tries.