The surgery will be performed on April 3 by elbow specialist Dr. Lewis Yocum at the Kerlan-Jobe Clinic in Los Angeles. Soria made the decision after considering his options for a few days.
"It's always a challenge, even the first time," Soria said in the Royals' clubhouse on Friday afternoon, "but right now, I'm feeling good. My mind is clear now, and I've just got to work hard, even harder than I was before, to get better and get out of this."
The surgery means that Soria, a right-hander, will be out at least for the season because the typical recovery time is nine months to a year, although it might be longer for a second surgery.
"It depends on the body and the rehab and everything. Only God knows about it," Soria said. "I'm just going to have my surgery and just try to get better."
Soria made the decision after getting three opinions, consulting with Yocum, head team physician Dr. Vincent Key and Dr. James Andrews of Birmingham, Ala.
"It's the right thing to do," Soria said. "They know what they're doing. Hopefully, I can have a clean surgery and have a good rehab to come back."
He had struggled throughout Spring Training, and finally last Sunday, he was taken out of the game and an MRI revealed damage to the ulnar collateral ligament in his pitching elbow.
Tommy John surgery is named for the Los Angeles Dodgers pitcher who had the first such procedure -- in which a tendon is taken from a different part of the body and attached to the elbow -- in 1974 by Dr. Frank Jobe. John came back to pitch 14 more years.
Soria had his first reconstructive elbow surgery in 2003 when he was a Minor Leaguer with the Dodgers. A second poses a new challenge.
"It's always bad for any person, but I'm taking it good," Soria said. "God knows why it happened to me, and it's in his hands and I'll move forward."
The confirmation of surgery means that the Royals closer's job will fall to either Greg Holland or Jonathan Broxton, with Aaron Crow also a possibility.
Broxton, the Dodgers' former All-Star closer, worked a perfect inning with two strikeouts against his old club in the Royals' 2-0 win on Friday.
"He was throwing 95, 97 [mph] today with an 89 mph slider. That's overpowering stuff," manager Ned Yost said. "Plus he's commanding the ball down in the zone and moving it in and out. It doesn't get much better than that."
Holland and Crow have also been impressive this month. Holland has 12 strikeouts in seven innings, and Crow has given up just two hits and two runs in seven innings.
"We've got time, we'll play it out," Yost said. "We can mix and match. We've got a bunch of really good options. We may, before the season starts, name a closer or we may not. I've got three guys that can close on any given night, so we may just go that route, too."
The Soria situation will also prompt a decision by club management in the future. The Royals hold options on Soria's contract for $8 million in 2013 and $8.75 million in '14. There is a $750,000 buyout in each case.
Soria, 27, has been one of the game's premier closers with 160 saves in five seasons with the Royals. He was an All-Star selection in 2008 and '10, the seasons that he had his best years with 42 and 43 saves, respectively.
Having two rounds of reconstructive elbow surgery is a challenge not taken on by many pitchers.
Yost believes that Soria has the grit to come back successfully.
"It's a tough thing, but he can overcome it," Yost said. "Guys that have his type of work ethic and his type of mentality can overcome it. I've seen guys do it. Lesser guys in their mental strength and mental makeup and work ethic, they never recover from it. It's too big, but I've got all the confidence in the world that Jack's going to recover from it."
Pitcher Chris Capuano, now with the Los Angeles Dodgers, had Tommy John surgery in 2002 and again in '08. He missed the '08 and '09 seasons but returned to find success with the Milwaukee Brewers in 2010. Last year, in the New York Mets' starting rotation, he was 11-12 in 33 games.
Reliever Hong-Chih Kuo was an All-Star for the Dodgers in 2010 after undergoing two Tommy John procedures. He was released by the Seattle Mariners this spring.
Other pitchers including Jason Isringhausen, Doug Brocail, Scott Williamson, Al Reyes, Darren Dreifort, Shawn Kelley and Mike Lincoln have had two such surgeries with varying degrees of results. Jose Rijo had it done three times before his career ended.
Outfielders Xavier Nady and Jay Payton were among the position players who have returned to play after two Tommy Johns. Catcher Vance Wilson had two surgeries, but his comeback fell short with the Royals in Spring Training two years ago.
Wilson, now manager of the Royals' Class A Wilmington team, noted that his situation was different because his two surgeries came within about a year of each other. Soria's second surgery will come about nine years after the first.
"His elbow was more back to normal by that point," Wilson said.
Wilson said the rehabilitation process is the most important item in recovery. His first rehab was a failure because the elbow blew out again, but his second, under the Royals' medical team, turned out much better.
"The rehab is everything," Wilson said. "He's lucky to be in a system under not only [head athletic trainer] Nick Kenney, but with [assistant trainer] Kyle Turner. Kyle oversaw my second one when I was here, and he's one of the best. That, to me, is the biggest thing."
For his part, Soria is confident that he can come back and pitch successfully.
"I'm sure I can," he said.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.