Chesterfield striker David Reeves scored twice to earn his side their first win in 11 games and put a severe dent in Plymouth's play-off chances.
Reeves pounced in the 17th minute just seconds after Pilgrims front man Marino Keith had cancelled out Steve Payne's early opener for the home side.
And Reeves struck his second four minutes into the second half to seal the points despite a late fightback from the visitors after Keith completed his own double 16 minutes from time.
After the game delighted Chesterfield assistant boss Lee Richardson said: "We're all incredibly relieved to finally get another win. Throughout the bad run the players have always given 110 per cent so they really deserve this result.
"Plymouth played the best football today but football isn't our priority at the moment, it's the results that count.
"I've criticised the fans in the past but they were magnificent today and won us the game.
"I want to pay tribute to them because it was very tense but they lifted us and they were the 12th man.
"We've got ten games left and just have to ensure that we get the points that will keep us up as quickly as possible because we don't want it to go down to the last couple of games of the season." The Spirieites started well and it was no surprise when Payne headed Rob Edwards' corner past Roman Larrieu in the tenth minute.
Keith levelled matters on the quarter hour when he converted Jason Bent's cross from six yards but Reeves restored Chesterfield's lead moments later from close range after good work by Chris Brandon.
Reeves struck again four minutes after the break seemingly to seal the win and despite Keith's second in the 74th minute the home side held out for a vital win which eased their relegation fears.