Spain, who survived double overtime against Australia to reach the final, led throughout in Beijing to win international basketball's biggest prize a second time.
The previous occasion was in 2006 with the two Gasol brothers, Marc and older sibling Pau, on the team.
Pau did not feature in China because of injury.
The latest triumph was particularly sweet for the 34-year-old centre Gasol, who three months ago also played a key part in the Toronto Raptors' run to the NBA title.
Gasol, who had 14 points, seven rebounds and seven assists, joins Lamar Odom, a double winner in 2010 with the United States and Los Angeles Lakers.
"What can I say? How does it sound to you?" Gasol told reporters of his personal feat.
"I feel very fortunate to be in this position, to play this game and help these guys.
"All of the things you sacrifice, it's worth it... what a year, what an amazing year."
Surprise finalists Argentina had not triumphed since they hosted the inaugural World Cup in 1950.
As a contest, the final was over by the fourth quarter -- although the Argentines did rally to reduce Spain's previously mighty lead for a time.
Fans of both teams had made it feel more like a football match, decked out in their national colours, chanting loudly and refusing to sit down.
Spain, for whom Ricky Rubio of the Phoenix Suns was afterwards named the tournament MVP, surged into a 14-2 lead.
Led by their slick-haired Italian coach Sergio Scariolo, Spain were up 21-14 going into the second quarter and increased their advantage to 43-31 at half-time.
With Rubio prominent, drilling 20 points, Spain never looked like surrendering their lead, repeatedly thwarting Argentina's suffocated offence.
Gasol said that Spain's defence, which limited Argentine talisman Luis Scola to eight points, was the bedrock of their victory.
"Defensively we improved game by game, our concentration, our determination, our consistency," he said.
Several of the Spain players had tears in their eyes as they collected the trophy.
Argentina's coach Sergio Hernandez said the better team won.
"No excuse, we were not tired, we were not satisfied because we wanted to win," he said.
"For me, we won the silver medal, we didn't lose the gold medal.
"I feel very proud of my players."
- Australia's wait goes on -
France roared back after half-time to defeat Australia 67-59 and claim a second World Cup bronze in a row -- and extend the Boomers' long wait for a major medal.
Turkish-based guard Nando De Colo led all scorers with 19 points for France and Nicolas Batum had nine points, six assists, three rebounds and three steals.
The French, one of the tallest teams at the tournament, defeated reigning two-time holders the United States in the quarter-finals, but then lost heavily to Argentina.
"For us it's something very, very special and important we did it after a very difficult first half," French coach Vincent Collet said.
"Many teams could have given up, even easy shots we were missing in the first half.
"We started to move the ball better in the second half and that's why we won this game."
It is still the best finish for the Boomers, who had never gone beyond the quarter-finals at 11 previous World Cups, but they are yet to claim a medal at the worlds or Olympics.
Deposed champions the United States, who were missing their elite names, finished seventh, their lowest position in tournament history.
They did, at least, qualify to defend their Olympic title in Tokyo next summer.
With 32 teams, this was the biggest-ever Basketball World Cup.
The next one will be in 2023 in Japan, Indonesia and the Philippines.