Flemming grew up in Alexandria, Virginia, listening to current Giants partner Jon Miller call Baltimore Orioles games. In 2004, Flemming began his first full year as an announcer for the team, working with Miller, Duane Kuiper and Mike Krukow on San Francisco station KNBR and the Giants Radio Network. He currently splits time between the Giants' radio and television broadcasts.
After graduating from St. Stephen's & St. Agnes School in 1994, Flemming received bachelor's and master's degrees in classics from Stanford University and a master's degree in broadcast journalism from the S.I. Newhouse School of Communications at Syracuse University. While at Stanford, Flemming broadcast Stanford Cardinal baseball, men's and women's basketball, and football and served as Sports Director at KZSU. In 2000, he broadcast play-by-play for the Visalia Oaks and served as the assistant General Manager, before moving on to the Pawtucket Red Sox.
Flemming teamed with PawSox radio broadcaster Andy Freed for three seasons on the eight-station PawSox Radio Network. His rise in the baseball broadcasting industry was fast, as he went from Class-A ball (Visalia) in 2000 to Triple-A from 2001–2003 (Pawtucket) and finally the Giants.
In twelve seasons calling Giants games, Flemming has been a part of many memorable on-air moments.
On April 27, 2003, in his second ever major league broadcast, working as a fill-in for Jon Miller, Flemming broadcast the Phillies' Kevin Millwood's no-hitter against the Giants. In some ways it was an indication of the moments to come.
Barry Bonds provided several of those. On May 28, 2006, Flemming had the chance for his voice to go into the National Baseball Hall of Fame and Museum when he was set to call Barry Bonds' 715th home run, passing Babe Ruth for second place on the all-time home run list. However, as he was making the call, his microphone went dead:
Flemming, unaware of the problem, continued to make the call, but all listeners heard was about ten seconds of dead air. Only Duane Kuiper's call on Fox Sports Net's broadcast was sent to the Hall of Fame. On September 23 of the same year, during Flemming's third-inning call of a game against the Milwaukee Brewers at Miller Park, Bonds hit a home run off left-hander Chris Capuano. This was Bonds' 734th career homer (26th for the season), which broke Hank Aaron's record for National League home runs. (Aaron hit his last 21 homers as an American League player.) Eventually on August 4, 2007, Flemming was able to call Bonds' record-tying 755th home run in San Diego on the radio against the San Diego Padres.
That call of #755 proved to be a notable one in a weekend of milestone moments for Bonds and Alex Rodriguez. Later that week, the New York Times sports media critic Richard Sandomir wrote of the collection of broadcasts that past weekend,
"But the best one on radio or TV came from Dave Flemming, the Giants’ radio announcer, who said clearly and excitedly on KNBR: "Bonds swings, 2-1 pitch. He drives one to left. Going back on the ball is Hairston. It's gone. Off the facing of the second deck. And Barry Bonds has equaled baseball's all-time home run record: 755 for Bonds."
On July 14, 2006, for a Friday night home game, Flemming made his television broadcast debut for the Giants. Since then, he has appeared both on NBC Sports Bay Area and KNTV during the baseball season.
Other milestone broadcasts Flemming contributed to include the calls of Greg Maddux and Randy Johnson's 300th pitching victories, and the Giants' Jonathan Sánchez's no hitter against the San Diego Padres on July 11, 2009.
On November 1, 2010, during the seventh inning in Game 5 of the World Series at Rangers Ballpark, Flemming made the winning home run call that eventually sealed the Giants' win, and thus the World Series:
On June 13, 2012, Flemming made the radio call of the final out of Matt Cain's perfect game, the first in the history of the Giants. In 2013 Flemming (along with Kuiper and Miller) won an Emmy for his coverage of the perfect game.
Later that season, on October 28, 2012, Flemming made the call for the final out of the 2012 World Series.
Starting in 2008, Flemming began broadcasting Stanford Cardinal football and basketball. He spent three years as the voice of Stanford basketball on the radio, and six years in that capacity with Stanford football before leaving the Stanford broadcasts to concentrate on his network work.
The period Flemming served as the voice of Stanford football coincided with perhaps the most successful stretch in the school's football history. Flemming's first broadcast on the Stanford radio network was the epic upset of #1 ranked USC on October 6, 2007. Over the next six seasons, Flemming was behind the microphone for the record performances of Toby Gerhart and Andrew Luck, and for three BCS bowl appearances, including a Rose Bowl victory over Wisconsin on January 1, 2013.
Flemming became a regular College Basketball on ESPN announcer in 2010, after having called a couple of games for the network the previous season. He primarily works Pac-12, Big 12, and WCC games for ESPN, teaming with Sean Farnham, Fran Fraschilla, and other analysts.
He has also called baseball for ESPN and ESPN Radio, and worked a season calling college football games for the Pac-12 Network in 2012 before shifting to College Football on ESPN in 2013. Also in 2013, Flemming began calling NBA games on ESPN Radio and contributing to Little League World Series coverage on ESPN and ABC. In 2015, Flemming began calling NFL games for ESPN Radio as well. In 2016, he began calling select Monday Night Baseball games for ESPN, as well as College Football Thursday Primetime games.
Flemming and his wife, Jessica, live in San Francisco with their identical twin daughters Katie and Carter and their son David Henry.