Ortiz, 43, was shot in the back by a motorcyclist at the club Dial Discotheque in Santo Domingo, Dominican National Police spokesman Felix Duran Mejia told CNN.
"The bullet went through his stomach," he said, adding that Ortiz's condition was "confidential."
Multiple people have been detained in connection to the shooting, he said.
His father, Leo Ortiz, confirmed the shooting to ESPN.
"They called to tell me that David is injured and that they took him to a medical center, but they did not tell me how he is or exactly where he was transferred," he said.
The Boston Red Sox organization said it was informed by Ortiz's family that its former player was being treated at Santo Domingo's Clinica Abel Gonzalez clinic for "a gunshot wound to the lower back/abdominal region."
"We have offered David's family all available resources to aid in his recovery and will continue to keep them in our hearts," the storied baseball organization said.
Meanwhile, the baseball world has been converging on Twitter to show their support for "Big Papi."
And Nestor Cortes of the New York Yankees remarked that the incident shows how danger can come to anyone, no matter who you are.
"It's crazy to hear what happened to David Ortiz," he said. "It goes to show you that anyone can be in danger at any time no matter your status. Get well soon, Big Papi. I'm praying for you."
Ortiz, a native of Santo Domingo, retired from Major League Baseball in 2016 after 20 years in the league, during which he won three World Series championships, was named the World Series MVP in 2013 and won the AL Silver Slugger title seven times, according to MLB.com.