Alzner set the record Wednesday when he took the ice against the Philadelphia Flyers.
The 27-year-old has played in every game since the start of the 2010-11 season, when Alzner played 14:09 in a 4-2 loss to the Atlanta Thrashers.
The previous record holder was Bobby Carpenter, also a defenceman, who played his 422nd consecutive game with the Capitals in 1986.
Alzner was drafted fifth overall in 2007. He played in parts of the 2008-09 and 2009-10 seasons, dressing for 30 and 21 games respectively.
Coming into Wednesday night's contest, the Burnaby, B.C. native had 97 points (15 goals, 82 assists) in 473 career NHL games.