Blackett, 20, was handed his United debut by Louis Van Gaal on the opening day of this season and has since made a further nine Premier League appearances.
The young defender has signed a contract extension that will keep him at Old Trafford until 2017, with an option of a further year.
Blackett told United’s official website: “I’m thrilled to have signed my new contract.
“I have supported United all my life and have been here since I was eight years old. To come through the Academy and make my debut this season was a dream come true.
“I want to keep improving within the first-team squad with the help of the manager, coaches and the players around me.”
Meanwhile, Reece James has also put pen-to-paper on a contract extension. The left-back made his United first-team debut in the humiliating 4-0 Capital One Cup defeat to Milton Keynes Dons earlier this season.
But it appears the United faithful aren’t overly excited about two of their academy products signing for an extended period, with some even suggesting van Gaal is prioritising deals for the wrong players…
Great to see United youngsters signing new contracts, but the ones we really want to see commit are Pereira and De Gea #mufc
— Joel Skinner (@joelskinner14) February 26, 2015
Actually disappointed Blackett has signed a new contract. Liability. McNair and Thorpe are miles better #mufc
— Alex Meechan (@Alex_Meechan88) February 26, 2015
— Dec Fox (@Dec_Fox) February 26, 2015
— Paul N (@PaulN84) February 26, 2015
Although we’re not exactly surprised with that reaction…