The new deal will see the 22-year-old remain at Bloomfield Road until at least June 2026- with an option for a further 12 months also included.
After returning to the Seasiders in the summer after a season-long loan with Forest Green Rovers, Casey has featured 16 times so far this season for Neil Critchley’s side, producing a number of standout performances.
Discussing his new deal, he told the club: “I'm really happy to have got this done.
"I've really enjoyed my football so far this season and am looking to really push on now.
"I think my game has developed a lot since I joined the club two years ago.
"Playing regularly is all any player wants to do, and I've been fortunate enough to be involved a lot - both this season and last season at Forest Green.
"It's taken my game to another level, and hopefully I can keep progressing.
"I've loved every minute playing in tangerine, and will continue to work hard for the club and the supporters week-on-week."
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Casey joined the Seasiders back in 2021, after coming through the Leeds United youth academy.
During his first campaign with the club, he made a handful of appearances and claimed his first ever senior goal.
While on loan at the New Lawn Stadium last season, he made 48 appearances for Forest Green and was named as their player of the year.