Preller, who has spent the past 10 seasons in the Rangers' organization and most recently served as the team's assistant GM, beat out three other finalists to replace Josh Byrnes, whom the Padres fired in June following an uninspiring 2 1/2-year run.
The 37-year-old Preller helped build the Rangers into one of the American League's most successful teams over the past five seasons, with Texas having won 90 or more games in each of the previous four years and reaching the World Series in back-to-back seasons in 2010 and 2011.
"It's an honor to have been selected for this position," said Preller. "I'm grateful for the faith [lead investor] Peter [Seidler], [executive chairman] Ron [Fowler] and [chief executive officer] Mike [Dee] have shown in me. I'm looking forward to meeting our baseball operations staff and getting right to work, with the goal of building a championship organization for San Diego."
Preller, a Cornell graduate and college roommate of current Texas GM Jon Daniels, has particularly made his mark in the area of international scouting, having been instrumental in the Rangers landing such impact players as Yu Darvish, Jurickson Profar, Leonys Martin and Rougned Odor on the foreign market.
"Padres ownership is thrilled to welcome A.J. Preller to the Padres family," said Seidler. "His balance of experience, knowledge and energy makes him the ideal person to lead our baseball operations as we work to build a consistent winner in San Diego."
The Padres initially interviewed eight candidates following Byrnes' dismissal on June 22, then narrowed that field down to Preller, Yankees assistant GM Billy Eppler, Red Sox assistant GM Mike Hazen and MLB senior vice president of baseball operations Kim Ng.