Late goals from Kazenga LuaLua and Jesse Lingard confirmed Yeovil's relegation from the Sky Bet Championship and fired Brighton back into the play-off places.
Substitute LuaLua struck with 11 minutes left and Lingard in stoppage time to secure a 2-0 win for the hosts and send Yeovil back to League One after one season.
The Glovers had arrived on the south coast already resigned to their fate, needing to win their remaining two games, hope everyone else around them lost theirs, and engineer a 13-goal swing.
But the Somerset side, who continue to punch above their weight while revelling in the tag 'Little Old Yeovil', were determined not to go away quietly and a battling display nearly ruined Brighton's chances of exiting the Championship in the opposite direction.
However, the Seagulls eventually ensured they climbed back into the final play-off spot, two points above Reading who play Doncaster on Saturday.
Yet Yeovil almost stunned the hosts after a quarter of an hour when Ruben Palazuelos crashed a superb effort from 25 yards against the crossbar.
The Seagulls were able to welcome Andrea Orlandi back into their side after two months on the sidelines, but the former Swansea winger looked a little rusty as he missed two gilt-edged chances in the space of two minutes.
First Lingard outstripped the Yeovil defence and crossed towards Leonardo Ulloa, but when the ball came back to Orlandi 12 yards out he blazed wide.
Moments later Will Buckley chipped the ball into the area where Orlandi dived to meet it in front of goal, but again the Spaniard was off target.
Brighton survived a scare in the 35th minute when keeper Tomasz Kuszczak came out to punch Jamie McAllister's free-kick from the halfway line, and completely missed it, but Lewis Dunk had got back on the line to prevent a bizarre goal.
The Seagulls piled forward throughout the second half but still their finishing was wayward.
Ulloa missed two headers in quick succession and Orlandi's attempted backheel in front of goal ended with the ball flying through his legs.
Brighton desperately needed a lucky break and they got it in the 79th minute when LuaLua aimed for Ulloa in the penalty area.
Once again the ball missed its intended target, but this time with the perfect outcome for Brighton as Town keeper Marek Stech was fooled by Ulloa's out-stretched leg and the ball nestled in the corner for a fortuitous goal.
Lingard doubled the lead, perhaps harshly on Yeovil, when he tucked away Solly March's pull-back moments before the end.