St Mirren bagged their first home Premiership win since early February to cement their place in the top flight next season.
Former Saints midfielder Charlie Adam did his old side a huge turn when he gifted the hosts an unbelievably easy opener. His hospital pass across his own box was duly fired in by Alex Greive, who couldn't quite believe his luck when the ball reached him unmarked to slot home.
Dundee battled back and threatened an equaliser early in the second half, with Jak Alnwick pulling off two brave saves to keep the Buddies ahead.
And striker Curtis Main slammed a sensational strike into the top corner to make the result safe - his first goal in the stripes since September couldn't have been hit any sweeter.
Retiring Saints chief executive and club legend Tony Fitzpatrick was given an emotional half-time send off by the home support, with the victory allowing the club to fully plan for Premiership football in his absence next season.
St Mirren made one enforced change to their starting XI that sealed last weekend's crucial win against St Johnstone, with Ethan Erhahon replacing injured Wolves loanee Connor Ronan.
Winger Jordan Jones was also unavailable after returning to parent club Wigan Athletic for treatment, with 16-year-old academy kid Aiden Gilmartin among the Saints substitutes.
The Buddies couldn't have asked for a better start when they were handed a gift-wrapped opening goal with just four minutes on the clock.
Dundee skipper Adam has made a career out of his sublime passing ability, but his horrendous cutback along his own six-yard box allowed Greive to nip in and break the deadlock.
Young New Zealand international Greive was impressive in the opening stages. He latched onto an excellent through ball from Ethan Erhahon but couldn't quite squeeze his cross into the Dundee box.
St Mirren were dominating and only a superb save from Harry Sharp stopped the hosts from doubling their lead.
A pinpoint cross from Alex Gogic picked out Curtis Main, who produced a looping header that was just tipped past the post by the young stopper.
Greg Kiltie was next to try his luck, fizzing a low strike just wide of the keeper's right post as the Buddies pressed hard for a second.
Dundee were almost handed a gift of their own when Conor McCarthy's misplaced pass eventually resulted in a free-kick on the edge of the Saints' box. Adam lined up a shot at redemption but could only fire into the wall, with his follow up effort blocked - much to the delight of the home faithful.
Richard Tait picked up the first booking of the game for a cynical challenge on Jordan Marshall that would certainly be filed under the topic 'taking one for the team' on a rare foray forward by the away side.
McCarthy powered a header over the bar when he probably should have done better after being picked out superbly by Scott Tanser.
And just before the half-time break the Buddies players and supporters were screaming for a penalty. A flowing passing move saw Main set up Kiltie, who in turn slipped in Greive.
The striker went down under pressure in the box from Ryan Sweeney, but referee David Dickinson was certain no foul was made and waved play on.
The Saints cruised into the half-time interval on the back of what was one of their most comfortable 45 minutes in Paisley for some time.
Dundee returned from the break with a fire lit under them and Jak Alnwick pulled off a sublime save to keep his side ahead from Sweeney's powerful header.
The Buddies keeper had been a virtual spectator in the first half but was called into action again shortly after when a goalmouth scramble from a corner eventually fell towards him. He bravely grasped hold of the ball under extreme pressure.
Dundee looked like threatening an equaliser, but it was St Mirren who doubled their lead in sensational style.
Curtis Main picked the ball up from Marcus Fraser's switch on the left side of the box before lashing an unstoppable strike into the top corner past Sharp.
Main almost picked up a brace with a downward header, but this time Sharp was equal to his effort.
The rest of the second half was without much goalmouth action but still dominated by the Buddies, with Stephen Robinson delighted to finally bag his first home victory since replacing Jim Goodwin as the home side cruised to all three points.
