Selected by the San Jose Sharks in the third round (No. 94) of the 2004 NHL Draft, Greiss is the first Germany-born goalie to play at least 100 NHL games.

After Greiss was drafted, he remained in Germany for two more seasons and at age 20 played one game for his country at the 2006 Torino Olympics, when he made 35 saves in a loss to Canada.

He attended his first training camp with San Jose prior to the 2006-07 season and played most of the season with Worcester of the American Hockey League, finishing 26-15-2 with a 2.61 goals-against average and .912 save percentage in 43 games. Greiss returned to Worcester for the 2007-08 season but was called up by the Sharks and made his NHL debut against the Anaheim Ducks on Jan. 13, 2008, making 25 saves in a 4-3 overtime loss. He played all of the 2008-09 season with Worcester, going 30-24-2 with a 2.47 GAA and .910 save percentage in 57 games.

Greiss played 2009-10 in San Jose backing up Evgeni Nabokov and went 7-4-1 with a 2.68 GAA and .912 save percentage. He also played three games for Germany at the 2010 Vancouver Olympics.

After one season with Brynas of the Swedish Elite League, Greiss returned to San Jose for two more seasons. He earned his first NHL shutout against the Colorado Avalanche on Jan. 26, 2013, when he made 24 saves in a 4-0 win.

Greiss signed as a free agent with the Phoenix Coyotes for the 2013-14 season and went 10-8-5 with a 2.29 GAA and .920 save percentage in 25 games. He played 20 games with the Pittsburgh Penguins in 2014-15, finishing 9-6-3 with a 2.59 GAA and .908 save percentage.

The Islanders signed Greiss to a two-year contract July 1, 2015. He split the goaltending duties with Jaroslav Halak until the latter sustained a lower-body injury March 8, 2016, making Greiss the unquestioned starter. He finished with NHL career highs in games (41), wins (23) and save percentage (.925), then helped the Islanders clinch a berth in the Stanley Cup Playoffs and win a series for the first time since 1993, when he allowed four goals over the final three games of the Eastern Conference First Round against the Florida Panthers, Greiss. He later represented Team Europe at the World Cup of Hockey 2016.

Greiss signed a three-year contract with the Islanders Jan. 30, 2017.

In 2018-19, Greiss and Robin Lehner won their first William M. Jennings Trophy, presented "to the goalkeeper(s) having played a minimum of 25 games for the team with the fewest goals scored against it." Greiss played 43 games and went 23-14-0 with a 2.28 GAA, .927 save percentage and five shutouts.

Greiss played two seasons for the Detroit Red Wings before signing a one-year, $1.25 million contract with the St. Louis Blues on July 13, 2022.

NOTES & TRANSACTIONS

• Signed as a free agent by Hannover (Germany), November 20, 2012.
• Signed as a free agent by Phoenix, July 5, 2013.
• Signed as a free agent by Pittsburgh, July 1, 2014.
• Signed as a free agent by NY Islanders, July 1, 2015.
• Signed as a free agent by Detroit, October 10, 2020.
• Signed as a free agent by St. Louis, July 13, 2022.