Known for his ability to hit the three-pointer, he attended the University of Florida from 1998 until 2000. As a sophomore, Miller led the Gators to the 2000 NCAA Championship game, losing to Michigan State. He hit perhaps the most dramatic shot of the tournament that year in the opening round against Butler. As the fifth-seeded Gators trailed the underdog Bulldogs by one, Miller drove to the basket and laid it in as time expired. That summer, he was taken with the 5th overall pick in the NBA Draft by the Orlando Magic. Miller won the 2001 NBA Rookie of the Year Award while being the only first-year player to appear in all 82 regular season games.
He was traded to Memphis midway through 2002–03 NBA season. He was the recipient of the NBA Sixth Man of the Year Award for the 2005–06 season. He averaged 13.7 ppg 5.4 rpg 2.7 apg while shooting 47% from the field and 41% from three-point range, while playing 30.6 minutes per game.
On January 3, 2007 Miller made nine three-pointers in a win over the Golden State Warriors, breaking Sam Mack's Grizzlies franchise record of eight in a game set in February 1999. The two previous games Miller hit seven threes. This made him the first NBA player to hit at least seven three-pointers in three consecutive games since the Dallas Mavericks' George McCloud achieved it in 1996. Miller holds the Memphis Grizzlies franchise record for most points scored in a single game, with 45 on February 21, 2007, against the Golden State Warriors.After the 2006–07 NBA season, Miller was announced as a member of the USA Basketball team.
On June 26, 2008, Miller, Brian Cardinal, Jason Collins, and the 5th pick of the 2008 NBA Draft, Kevin Love, were sent to Minnesota in exchange for Marko Jaric, Antoine Walker, Greg Buckner and the 3rd pick O. J. Mayo.
On June 23, 2009, Miller and Randy Foye were sent to the Washington Wizards for Oleksiy Pecherov, Etan Thomas, Darius Songaila and a first round draft pick. Miller suffered a shoulder injury and missed a few games during the early part of the 2009–10 NBA season.
On July 15, 2010, Miller signed a five-year $25 million contract with the Miami Heat. He injured his thumb while guarding LeBron James in practice during the pre-season, sidelining him for several weeks. Miller officially returned to the Miami Heat lineup on December 20, 2010, in a home game against the Dallas Mavericks. Miller got his first start on January 22, 2011, due to a Dwyane Wade illness, and contributed with a season-high 32 points in a win over the Toronto Raptors.
On January 17, 2012, Miller made six of six three point field goals in a victory over the San Antonio Spurs to finish with 18 points in his return to the Heat, after missing several games because of an injury.
In Game 5 of the 2012 NBA Finals against the Oklahoma City Thunder, Miller made seven three-pointers, setting the NBA Finals record for most three-pointers by a reserve. He had not made any three-pointers in the previous four games of the series. He finished with 23 points, 5 rebounds and a steal in Game 5. Miami would go on to win the NBA championship in five games.
Miller was inserted into the starting lineup during Games 5 to 7 of the 2013 NBA Finals against the San Antonio Spurs to help space the floor. He hit a 3 pointer in Game 6 while wearing one shoe. The Heat won the series in Game 7 on June 20, 2013, giving Miller his second championship
Mike and his wife, Jen, have three kids: two sons, Mason and Mavrick, and a daughter, Jaelyn. His daughter was born during the Heat's appearance in the 2011 Eastern Conference Finals with a serious health issue stemming from pregnancy complications; he spent the first several days of his daughter's life shuttling between practices, games, and the hospital. He once owned a Java Macaque named Sonny. He often tells the story in which his monkey escaped from his room: "You would always put him in his room, and then we'd lock the door, and then we'd put the dogs out, and then we'd lock the front door. Well, he found out how to unlock doors, unlocked his door, went downstairs, let the dogs in the house and opened the front door. About an hour later we got a call from our neighbors, saying, 'Your monkey is riding your dogs around the neighborhood.'...I said, 'C'mon y'all, y'all got to get in the house.