According to the Pirates' official release, the surgery was performed by Dr. James Andrews in Pensacola, Fla.
Morton was placed on the disabled list on June 1 with inflammation in the elbow. Following a couple of instances of flat-ground throwing, Morton attempted his first bullpen session on Sunday. Persistent elbow pain from that prompted a doctor's visit, resulting in the ligament-tear diagnosis.
Reliever Jason Grilli, who missed the entire 2002 season while recovering from Tommy John surgery, said he offered Morton words of encouragement about what figures to be a long, slow and lonely process.
"It's never a fun bit of news, but it's kind of like he's just missing time now," Grilli said. "I feel horrible for him, but I know he's going to be fine. He's going to be stronger than ever."
Typical recovery time puts Morton on schedule to return in the middle of the 2013 season. The 28-year-old will be arbitration-eligible for the final time this offseason, and agreed to a $2,445,000 contract last winter to avoid a hearing.
Tommy John has become an increasingly popular procedure across Major League Baseball in recent years, and many pitchers have been able to return to their normal form following the operation.
"You go around the league and there's more guys with the zipper on the elbow than there's not," Grilli said. "Usually the thing that's the hardest is just getting confidence and control in your pitches, and just trusting that it's healthy again."
Morton's season was delayed by the last leg of his recuperation from hip surgery in October. He made his first start on April 14 and fashioned a 2.65 ERA through his first three outings.
Things began to go sour for Morton on May 1, when he lasted only 4 1/3 innings in a 10-7 loss to the Cardinals. From that point on, he lost five of six decisions while being hit at a .331 rate, and with an ERA of 5.67.
Most telling, and likely as a result of not being able to command his trademark sinker with the weakened elbow, Morton allowed five home runs to right-handed batters in 100 at-bats. Last season, he gave up one homer to a right-handed hitter in 381 at-bats.
"His sinker might be even dirtier than it was before," Grilli said.
Greg Luca is an associate reporter for MLB.com. Tom Singer contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.