The team announced Miniak during the seventh-inning stretch of Saturday's 3-1 win over the Giants.
"We want to thank everyone who tried out for sharing their time and enthusiasm with us over the past few months," Padres president and CEO Mike Dee said in a press release. "Our intent for this process was to offer a true open casting call, with the possibility of discovering talent in even the least expected of places. In finding Alex, we accomplished that goal."
Miniak edged two other finalists, Sam Chin and Todd Leitz, after each had the opportunity to announce a full game at Petco Park this week.
"Alex has the iconic voice that we were looking for and we're excited to welcome him to the Padres family," said Wayne Partello, Padres senior vice president and chief marketing officer. "This was not an easy decision. There was a tremendous pool of talent, and the final three, especially, were all impressive. But in the end, Alex has the right voice to take us into the next era of Petco Park."
The list of hopefuls started at more than 800 and was narrowed down to 50, then 30, then 10, with the help of a fan vote, and finally to the three finalists.
Miniak, who is a senior account executive with Gigunda Group, will move to San Diego, leaving his current role as the public-address announcer for the New Hampshire Fisher Cats, the Double-A affiliate of the Toronto Blue Jays.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.