Birmingham and Doncaster both failed to win away from home, meaning The Seasiders' fate was sealed elsewhere, as already-safe Charlton put in an accomplished second half display at Bloomfield Road.
A hat-trick from Callum Harriott ensured the visitors ran out comfortable winners in the end, but both clubs will meet in English football's second tier again next season.
Barry Ferguson's side had started the better side and squandered a number of good chances, but once The Addicks edged ahead there was no looking back.
Blackpool had dominated the first half, but failed to convert their chances. Tony McMahon tested Ben Hamer early on, before an in-form Stephen Dobbie dragged his effort inches wide.
Next the Scot twisted an turned his man, before seeing his powerful near-post strike palmed over by Hamer. Soon after Craig Cathcart headed McMahon's dangerous free-kick just over the bar.
Fresh from his assist last week, Isaiah Osbourne then embarked on a surging run, before crossing for Chris Basham, whose header was comfortably kept out, as the game remained goalless.
Charlton's best effort came from a set piece, with Dorain Dervite blasting a free-kick wide. But it was still The Seasiders dominating proceedings, next Andy Keogh left fly with a drive that sailed over the bar, as the two sides went in level.
With both Doncaster and Birmingham drawing at the break it meant nothing had changed in terms of Pool's danger.
Half Time: Blackpool 0 Charlton 0
The visitors came out for the second half improved, and Marvin Sordell stung the palms of Matt Gilks early on, while Keogh dragged an effort wide.
Ten minutes after the break Blackpool carved out their best chance yet, with Dobbie playing a one-two with Basham, before firing wide of Hamer's left-hand post.
For all their chances, Blackpool somehow found themselves behind on the hour mark, as Charlton edged ahead against the run of play.
Harriott raced clear onto Sordell's through ball, before clipping his effort beyond Gilks. But Bolton's goal at home to Birmingham arrived almost simultaneously.
That goal sprung Blackpool into life as Keogh set up Bishop, but the midfielder's effort was diverted over by brave Charlton defending.
That was the Irishman's last involvement, with Ricardo Fuller replacing him against his former club, before Tom Barkhuizen followed him on in place of Basham.
McMahon then bent a free-kick over the bar, but with nine minutes remaining The Addicks made the game safe.
Substitute Jonathan Obika's mazy run was too good for Blackpool's defence, and his cross was tucked home by the Harriott, who used his predatory instinct.
With six minutes remaining Elliot Grandin replaced Bishop, but with the the remaining time Chartlon only rubber stamped their victory.
Harriott was allowed to cut in onto his left foot inside the box, before firing into the Gilks' bottom corner.
It meant Charlton's victory was sealed, but fortunately so was Pool's status, as Doncaster dropped into League One after a 1-0 defeat at Leicester.
Full Time: Blackpool 0 Charlton 3
By Mark Ridgway