Presenting new leadership and a revamped sport, wrestling easily defeated bids from baseball-softball and squash to secure a spot in the program for the 2020 and 2024 Games.
The result capped a frantic six-month campaign by wrestling body FILA to save its Olympic status after the IOC executive board surprisingly cut it from the list of core sports in February.
"We are aware of our mistakes and they will not happen again," FILA President Nenad Lalovic said. "This crisis gave us the strength to change and we finally found out that we can change. This was the most valuable experience of all of this journey."
Wrestling received 49 votes to win in the first round of the secret balloting by the International Olympic Committee. Baseball-softball got 24 votes and squash 22.
"Wrestling has shown great passion and resilience in the last few months," IOC President Jacques Rogge said. "They have taken a number of steps to modernize and improve their sport."
The vote followed final presentations by all three sports, with Lalovic calling it "the most important day in the 2,000-year history of our sport."
Wrestling's reinstatement appeared virtually assured for months after IOC members acknowledged that the executive board erred by cutting the sport in the first place.
"I think what happened was what most people thought, that the previous decision was wrong," Puerto Rican member and presidential candidate Richard Carrion said.
Canadian women's coach Leigh Vierling was thrilled with the news.
"I woke up this morning so apprehensive, yet so excited. I was just such an amazing mix of emotion," he said. "The relief when the actual decision was phenomenal."
Wrestling goes back to the ancient Olympics in Greece and has been on the program of every modern games except 1900. The sport was caught off guard when it was axed by the board — a decision that surprised even most IOC members.
Raphael Martinetti resigned as FILA president within days of the IOC vote and was replaced by Lalovic.
FILA reworked its structure, giving women and athletes a role in decision making. It added two weight classes for women. It adopted rule changes to make the sport easier to understand and more fun to watch, and reward more aggressive wrestling.
Powerful countries and unlikely political allies like the United States, Iran and Russia threw their weight behind the campaign.
"Wrestling is not a new sport," Lalovic said. " But the wrestling we are presenting now is a new wrestling."
Wrestling was approved by the IOC on Sunday as an "additional sport" for 2020 and 2024. FILA's goal now is win back a place in the list of 25 "core" sports.
"We have to understand that in four years we will have to compete again to become a core sport," Lalovic said. "So we can't stop now. What we have to do in four years is more difficult, maybe."
With wrestling's return, no new sport has been added to the 2020 Games, defeating the original purpose of the IOC's program review process.
"The result is we are back where we started and they've spent a lot of time and energy, emotional or otherwise in a process that was pretty well doomed," Canadian member Dick Pound said.
Pound proposed postponement of the vote for five months to allow a new sport to get in, but that was rejected by Rogge and the rest of the delegates.
"This doesn't happen in the IOC too often, but that vote is to tell the executive committee, you made a mess of this and we're going to fix the mess and we've got to figure out another way forward," Pound said.
Wrestling's reinstatement was cheered by some of the biggest names in the sport.
"It's almost like you expected that to happen," former American Olympic gold medallist and coach Dan Gable told The Associated Press. "But we certainly didn't expect what happened in February to happen, and because of that you learn and work through the whole process."
Russian great Alexander Karelin called it "a big result for us and for the new guys who are coming (into the sport)."
"I think we have a great story, great history and Olympic traditions," Karelin said.
For the future, the IOC will consider tweaking the process, possibly juggling events and disciplines to make room for new sports, while keeping within the cap of 10,500 athletes.
"I think what will happen is we will take away some of the events from some sports in order to put a couple of new sports in," Norwegian member Gerhard Heiberg said.
Squash and baseball-softball could potentially get another chance to make it onto the 2020 program.
Squash was trying to make the Olympics for the third time. Men's baseball and women's softball merged into a single federation to try to return after being dropped for the 2012 and 2016 Games.
Don Porter, the American co-president of the World Baseball Softball Confederation, choked up and had tears in his eyes as he talked about receiving letters from young girls who were distraught when softball was dropped.
Porter broke down again later when he told reporters: " I feel like I let them down."
AP Sports Writers Stephen Wade and Tales Azzoni in Buenos Aires and Luke Meredith in Des Moines, Iowa, contributed to this report.
Follow Stephen Wilson on Twitter: http://twitter.com/stevewilsonap