Yeovil twice came from behind to win the game. Jordan Bowery gave Chesterfield an early lead, with Dominic Blizzard levelling.
The visitors went ahead again after 69 minutes, but goals from Keiran Agard (73) and Andy Williams (80) sealed all three points and relegates Chesterfield to League Two.
Yeovil Town won for a club record 8th time in a row. Bristol Rovers also won, Cheltenham drew and Bristol City lost in the Severnside derby.
There were wins today for both Bristol clubs and Yeovil Town. Swindon Town could only draw and Cheltenham Town slipped to defeat.
Bath have beaten West Country rivals Gloucester 32 - 5 in the LV= Cup.