Miller was the winningest American-born goaltender in NHL history from February 2019 until March 2024, when he was passed by Jonathan Quick.

He was selected to play for the United States in the 2010 Winter Olympics in Vancouver as the team's starting goaltender.

In the 2004–05 season, with the NHL not playing due to a lockout, he won 41 games for the Americans, tying Gerry Cheevers' record.

That season he was 10–4 in shootouts, with Martin Brodeur of the New Jersey Devils being his closest rival at 10 wins and 6 losses.

In 63 games played that season, Miller posted a .911 save percentage and a 2.72 GAA backing a more offensively-oriented team.

Miller earned a shutout, stopping 20 shots in a game following the death of his 18-year-old cousin, Matt, who had died the Monday before of a complication with a bone-marrow transplant.

At the close of the game, Miller raised his stick to the home crowd in tribute and received star honors for his effort in net.

The game was played at Ralph Wilson Stadium, home to National Football League's Buffalo Bills, in Orchard Park, New York.

Miller suffered a high-end ankle sprain on February 22, 2009, in a game against the New York Rangers, which kept him out of action until late March.

[9] The 2012–13 NHL season did not go well for the Sabres, as they finished 12th in the Eastern Conference and failed to qualify for the playoffs for the second consecutive year.

On February 28, 2014, Miller and forward Steve Ott were traded from the Sabres to the St. Louis Blues in exchange for Jaroslav Halák, Chris Stewart, William Carrier and two future draft picks.

[11] He would make his Blues debut along with Ott on March 3, stopping 23 shots in a 4–2 victory over the Phoenix Coyotes.

Miller became an unrestricted free agent on July 1, 2014, and signed a three-year, $18 million contract to become the starting goaltender with the Vancouver Canucks.

However, on February 22, Miller was injured after Jannik Hansen crashed into him, ending his night as he and Eddie Lack combined for a shutout over the New York Islanders.

[14] In his return to health, Miller was able to make his debut with the Ducks in a 4–3 shootout victory over the Carolina Hurricanes on October 29, 2017.

[15] On February 17, 2019, Miller became the winningest American-born goaltender in NHL history, surpassing John Vanbiesbrouck.

[16][17] On June 20, 2019, Miller was re-signed by the Ducks to return for a third season with the club,[18] agreeing to a one-year $2.235 million contract extension.

He led the team to a perfect 5–0 start, including a 5–3 win over gold-medal favorite Canada in the preliminary round, stopping 42 of 45 shots.

The five wins, including victories over Switzerland and Finland in the quarter-finals and semi-finals, respectively, brought the US to the gold medal game, where they faced Canada for the second time.

[25] Miller also won International Ice Hockey Federation (IIHF) best goaltender honors and was named to the All-Star team.

[30] In 2006, Miller, along with his father Dean, started the Steadfast Foundation which supports cancer patients and their families.