Carrick's existing deal was due to expire at the end of the current season, however the England international will remain under contract at Old Trafford until the end of next season.
Since signing for United from Tottenham in 2006, Carrick has made 376 appearances for the club, winning five Premier League crowns as well as the UEFA Champions League in 2008.
"[Carrick] is for me my second captain behind Wayne Rooney and he can also read the game as a team player so that's very important," Van Gaal told the club's official website.
"He has also an excellent pass forward. That's very important for me."
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