The win gave Spain an unassailable 3-1 lead before Nicolas Almagro beat Marco Chiudinelli 6-1, 6-3 in the dead rubber to make it 4-1.
Ferrer looked in control throughout Sunday's match at the Logrono bullring, breaking Wawrinka's serve twice before wrapping up the first set with a drop shot. The Swiss' strong net game gave him an early break in the second. But after Ferrer had fought back, Wawrinka was docked a point after losing his temper and smashing his racket, handing his opponent a decisive break point.
The Spaniard didn't lose another game as he closed out the match, extending his country's unbeaten run at home to 19 ties, dating back to 1999.
"We knew it was tough playing here against Spain," Wawrinka said. "We tried, but beating Spain at home is difficult. That's the Davis Cup."
The hosts had gone 2-1 up on Saturday after Tommy Robredo and Marcel Granollers beat Wawrinka and Yves Allegro in the doubles. In Friday's singles, Ferrer beat Chiudinelli and Wawrinka beat Almagro.
"No other country has the standard of tennis we have in Spain," Ferrer said. "We've played well in the home ties and that is crucial. What's more, we've done well in the doubles matches."
Both teams were without their best player, as Swiss No. 1 Roger Federer skipped the event and Rafael Nadal is struggling with a knee injury.
Spain is attempting to win its third straight Davis Cup title and will play away against France in the quarterfinals July 9-11. Spain has lost to France only once in six prior meetings - in their first series in 1923.
"This competition is the biggest there is," Ferrer said. "We're all motivated to win it again."
Spain ties Switzerland 1-1 in Davis CupRonaldo aims for double glory
