St Johnstone exposed struggling Dundee's defensive deficiencies at Dens Park to extend their winning run to four matches.
Gregory Tade shot the visitors in front only for Ryan Conroy to level from the penalty spot.
A Liam Craig strike had the Saints back in front before the interval.
And Steven MacLean extended the lead in the second half with a clever stooping header as the confident Saints took a grip on the game.
This was the first meeting of these River Tay rivals since 2009 and the absence had not made any hearts grow fonder as fans traded colourful insults during the lively early stages.
However, it was the visiting supporters who finished the day in fine voice having watched their team enjoy a comfortable win.
Dundee were first to threaten when a lovely touch from Jim McAlister nutmegged an opponent in the penalty area and the midfielder was unlucky to see his shot hit the legs of keeper Alan Mannus before spinning off the post.
Saints defender Steven Anderson was short with a headed back-pass, allowing Martin Boyle a tentative poke at the ball but Mannus was in close attendance and able to block.
The first sign of Dundee's frailties came when Iain Davidson misjudged a high ball over the top allowing Tade to get to the bye-line and feed the ball across goal but an unorthodox Matt Lockwood intervention allowed keeper Rab Douglas to gather.
More hesitancy in the home defence allowed Saints to take the lead as Craig was given ample space on the left of the penalty area to cut the ball across for Tade to slam his shot high into the net.
Dundee were level soon after when Frazer Wright was cautioned for blocking off Boyle after a period of pinball in the penalty area and Conroy tucked away the spot-kick.
Conroy then tried his luck with a swerving free-kick from 25 yards that Mannus had to tip over.
Dundee were looking menacing in attack but once again fell behind when Tade glanced on a cross from Chris Millar and Craig was able to squeeze in a shot from a tight angle near the back post.
With the home side showing no signs of improvement at the back, Craig sliced a shot high over the bar from 18 yards and a fierce strike from Nigel Hasselbaink, on for the injured Paddy Cregg, was smothered by Douglas.
Saints moved further ahead early in the second period as MacLean demonstrated a great poacher's instinct to crouch low at the back post and nod home a Wright header from a corner.
Tade headed over from another corner and MacLean saw his scuffed shot saved as cries of "olé" from the Bob Shankly Stand marked the visitors' dominance.
Tade nearly uprooted the goals with a thunderous low shot that cannoned off the base of Douglas's near post.
Murray Davidson dragged a close-range shot wide after MacLean did well to keep a looping delivery from Craig in play and Douglas had to look smart to stop another effort from Davidson.
The muscular Tade was causing the Dundee defence all sorts of problems and Douglas needed strong hands to repel another stinging shot.
There was one setback for the visitors late on as MacLean was stretchered off with a dislocated elbow after being grappled by Matt Lockwood in the penalty area.
Dundee duo Gary Irvine and Conroy both went close with shots in the final stages but by then most of the disappointed Dundee fans had left the stadium.