Past and present members of the organization, as well as the public, were on hand for the service.
Montgomery died last month at the age of 72 after a five-year battle with cancer.
He was remembered as the Phillies' No. 1 fan.
"What will we miss most about David Montgomery? The list is beyond today. We will miss the smile, the jabs, the competitiveness, the side conversations that were filled with honesty and inquisitive questions, and we will miss his overall presence. The room was always his whether he said anything or just walked into it full of life," Phillies broadcaster Tom McCarthy said.
"David was an amazing guy. His most lasting gift to the fans of Philadelphia is this stadium. He had a great part in deciding how this stadium would be built and he was determined to make it the most fan-friendly stadium in the major leagues, and I believe it is," former Pennsylvania Gov. Ed Rendell said.
Montgomery was one of the most admired executives in Major League Baseball.
Montgomery's career with the Phillies began in 1971, working in the ticket office during the day and helping operate the scoreboard at night. He was later named the marketing director and then director of sales. He was promoted to executive vice president after the 1981 season.
Montgomery presided over five division titles, two pennants and the 2008 World Series title.
"Whenever we'd have a charity event, me or any of the guys, he would be there," said former Phillies All-Star Ryan Howard.
Montgomery took a short leave of absence as president and CEO in August 2014 after he was diagnosed with cancer in May 2014. He returned January 2015 and remained active in this role until his passing, attending many of the team's 2019 spring training games in Clearwater, as well as this year's home opener at Citizens Bank Park.
He is survived by his wife, Lyn; three children, Harry, Sam and Susa; one granddaughter, Elizabeth and two grandsons, Cameron and Will.
CBS3's Dan Koob contributed to this report.
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