Manager Terry Francona said the pair will likely be the last of Boston's September additions, a group that already includes outfielders Brian Anderson and Joey Gathright, pitchers Michael Bowden and Junichi Tazawa, catcher George Kottaras and infielder Chris Woodward.
"Unless something really goes wrong," Francona said, "we have a pretty full room down there."
Francona said Lowrie is expected to be used "selectively" during the final weeks of a season that has been plagued by left wrist woes.
"He's on a program where he's still strengthening," Francona said of Lowrie, who is batting .143 with one home run and seven RBIs in 19 games this year. "We think he's a good player. It's just been kind of a crazy year for him."
Coming off a Spring Training in which he battled Julio Lugo to be the team's everyday shortstop, the 25-year-old Lowrie underwent left wrist surgery on April 21 and did not rejoin the Red Sox until July 18.
Lowrie's stay with the big club was short-lived, however, as he returned to the DL on Aug. 8 after being diagnosed with ulnar neuritis in his troublesome left wrist.
Brown, who has appeared in one game for Boston this season, hit .264 with two homers and 23 RBIs in 86 contests for the PawSox. The rookie backstop gives Francona another option amongst a corps of Red Sox catchers that also features Kottaras, Victor Martinez and Jason Varitek.
"I think the experience is great for him," Francona said. "He deserves it. It also gives us the ability to pinch-hit or pinch-run. When Victor is in the game at first, there's some hesitancy to move him behind the plate. We had to do it a few times early on, but this gives us the ability to pretty much do what we want."
John Barone is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.