Tommy Robredo and Feliciano Lopez upset Israeli doubles specialists Jonathan Erlich and Andy Ram 7-6, 6-7, 6-4, 6-2 to put champions Spain through to their fifth Davis Cup final in 10 years.
Juan Carlos Ferrero and David Ferrer had opened a 2-0 lead for the home side with crushing victories in Friday's singles before Robredo and Lopez gave Spain an unassailable 3-0 advantage in the best-of-five tie on the clay in Murcia.
Spain, winners in 2000, 2004 and 2008, will play Czech Republic at home in December's final after making light of the absence of injured world number two Rafael Nadal and Fernando Verdasco.
Czechs Radek Stepanek and Tomas Berdych, who both won in Friday's singles in Porec, paired up to beat Marin Cilic and Lovro Zovko and send the visitors through against Croatia.
"The Czechs are very dangerous and have beaten some very good teams already this year," Spain captain Albert Costa said at a news conference.
"Stepanek and Berdych have both been in the top ten and can adapt easily to any surface."
Israel had stunned 2006 champions Russia to progress to the last four for the first time and were relying on Erlich and Ram, 2008 Australian Open doubles winners, to keep alive their hopes of an unlikely victory.
After trading tie-breaks with the Israeli pair, Robredo and Lopez stepped up a gear to win the third set and grabbed a crucial break on the Erlich serve in the third game of the fourth.
The Israeli suffered a season-ending injury to his right elbow in 2008 and play was interrupted so he could have treatment on what looked like a recurrence of the problem.
Spain then broke again for 4-1 and sealed victory on their first match point when Robredo put away an angled volley.
Meanwhile Czech Republic reached the Davis Cup final for the first time when Radek Stepanek and Tomas Berdych beat Marin Cilic and Lovro Zovko 6-1, 6-3, 6-4 to open an unassailable 3-0 lead over Croatia on Saturday.
"This is an unbelievable success for our country," Czech captain Jaroslav Navratil told Croatian TV. "We made it to the final after 29 years and I am exceptionally proud of our players who put up a great performance in all three matches."
The former Czechoslovakia won the Davis Cup in 1980 by beating Italy with a team led by Ivan Lendl but this is the first time the Czech Republic have reached the final.
The Czech doubles pair won in two hours and 15 minutes in a contest that was much less difficult than their singles matches.