John Carlson was born on January 1, 1990 in Natick, Massachusetts. He was selected 27th overall by the Washington Capitals in the 2008 NHL Entry Draft.
Carlson played his junior hockey for the Indiana Ice of the USHL before joining the London Knights of the Ontario Hockey League for the 2008-09 season.
Carlson was part of the gold medal-winning American team at the 2010 World Junior Championships, where he scored the game-winning goal in overtime of the gold medal game against Canada.
Carlson made his NHL debut for the Capital. on November 21, 2009 against the Montreal Canadiens and would split time between Washington and their AHL affiliate in Hershey for the 2009-10 season.
At the 2014 Winter Olympics, Carlson represented the United States once again, helping them to a fourth place finish in the tournament.
During the 2014-15 season, Carlson broke out offensively and established new career-highs with 12 goals and 43 assists in 82 games. His 55 points were the sixth highest total amongst all NHL defenceman.