The announcement will come at 10 a.m. ET from the Yankees' spring training camp in Tampa, Fla. Rivera, who is coming off surgery to repair a torn ACL in his right knee, then will pitch against the Atlanta Braves. It will be Rivera's first appearance this spring.
The New York Post initially reported Rivera's decision.
Considered the greatest closer in baseball history, Rivera, 43, will retire as the all-time saves leader. He enters the 2013 season with 608 saves, seven more than Trevor Hoffman's career total.
Rivera's 42 postseason saves are nine more than the combined total of the next two on the list, Brad Lidge and Dennis Eckersley. Rivera has won five World Series rings with the Yankees, his only big league employer.
Rivera returned home this week for a personal matter, and was expected to rejoin the team Saturday.
"He is the greatest closer of all time," Girardi said. "There is no question in my mind. I have had the thrill of catching him. I was really there when he burst on to the scene and he was a dominant setup man, and then to see what he did as a closer was a thrill for me. I know there is a press conference on Saturday, and we'll go from there."
Hank Steinbrenner declined to say what would be announced at Saturday's news conference. But the Yankees co-chairman said he would like Rivera to remain involved with the team when he does end his playing career.
"If he wants to, that would be my preference," Steinbrenner said. "I think he'd be a great influence, even if it's only at spring training."
The thinking all spring has been that this season would be Rivera's last. Rivera has always said he wanted to tell the people most important to him before making any announcements about his future.
There had been a feeling that Rivera would call it a career after 2012: In spring training last year, he had hinted that it might be his final season. After getting hurt, though, he vowed to return. He injured his knee while shagging balls in the outfield before a game in Kansas City last May.
For years now, Rivera has struggled with his desire to be home with family and devote even more time to his work with his church.
"I can't say it surprises me," former Yankees manager Joe Torre said. "I think he was sort of in-between last year, before he got hurt. It didn't surprise me he wanted to come back, just based on who he is and what he represents."
Almost a quarter century ago, on Feb. 17, 1990, Herb Raybourn, then the Yankees' director of Latin America operations, signed Rivera as an undrafted free agent for $3,000. Rivera was not considered a top prospect until he developed what became his trademark cut fastball.
Rivera arrived in the majors in 1995. He started 10 games, going 5-3 with a 5.94 ERA. The Yankees decided he would be better as a reliever, and he was instrumental as the club's setup man in the team's 1996 run to the championship.
"I know as a player, I always counted backward, how many innings we needed from our starter because of what he was capable of doing," Girardi said. "There were times when he was a setup man where he would give you more than two innings, so if you could get to the seventh, the game was over."
In 1997, he became the Yankees' closer. Rivera's career ERA of 2.21 is the second-best in major league history among pitchers who have thrown 1,000 or more innings, according to the Elias Sports Bureau. Eddie Cicotte's 2.20 is the best.
The numbers Rivera put up never may be duplicated, either.
"A lot of people over the years have asked, especially when I go back to Japan, 'Who is the guy that you don't want to face, or the toughest guy to face?' " Yankees outfielder Ichiro Suzuki said through a translator. "He was probably the guy who would come up at the top of my list.
"To have the success that he's had, there's been nobody who has had this much success and there will be nobody in the future that has this much success with one pitch. Pitchers obviously try to throw to places that hitters will have a hard time hitting, placing the ball where a hitter doesn't want to have it thrown. But Mariano would just throw to where you are waiting for the pitch and you still can't hit it."
Information from The Associated Press was used in this report.