Left-back Blackett joined Blackpool in November and has impressed at Bloomfield Road since making the switch.
Now Paul Ince has persuaded his former club to let him keep Blackett until the New Year.
"The kid has done well," Ince said.
"He's only 19 but I think the last game and the game before he grew into his role. I think he'll only get better.
"He's better off playing in this environment and learning his trade."