The Seasiders have seven players unavailable for their clash with Nottingham Forest on Saturday and Jack Robinson's suspension and Chris Basham's injury have left them particularly short in the left-back department.
Robinson, himself on loan from Liverpool, was sent off against Blackburn last weekend and will miss the next four games after being dismissed twice already this term.
Boss Paul Ince has tried to solve his defensive dilemma by returning to former club United, who have sent 19-year-old Blackett on his first loan move.
"It's a decent move for me personally to get involved with the lads and play first-team football. Its an experience to get games to improve myself," Blackett told Blackpool's YouTube channel.
"I'm a full-back and I like to get forward and attack. I'm strong, fast, quick, have a good left foot and I just like to get involved in the play. Set-pieces are a bit of a specialty so I'll just be saving it."
United boss David Moyes spoke to Blackett before ratifying the move and will closely monitor his progress at Bloomfield Road.
Blackett added: "He said it's a good opportunity for me to put myself out there and just to enjoy it."