Goals from Kane Hemmings and Olly Crankshaw sent Dundee leaping over opponents Ayr into third place in the Championship.
Hemmings raced clear of the visitors’ defence as the game at Dens Park ticked into its 11th minute, shooting low into the net.
Substitute Crankshaw made sure with a goal two minutes into injury-time after he was found by Graham Dorrans’ cutback.
James McPake’s men have now gone six games undefeated – three wins and three draws – and are now tucked in behind Inverness Caley Thistle, who are four points ahead in second spot in the table.
Significantly, it was also another clean sheet for the Dens defence – their fifth in a row.
Dundee started brightly and deserved a result that keeps the momentum going at the club as the season heads into its crucial stage.
The Dark Blues had made two changes to the team that started the 0-0 draw between these sides at Somerset Park on Saturday.
Jordan McGhee failed to recover from his dead leg and was replaced by Andrew Nelson, while Cammy Kerr dropped to the bench and Christie Elliot took his place.
Also a sub was 18-year-old goalie Harrison Sharp, with Jack Hamilton missing the game because of the birth of his child.
It was a chilly evening at Dens and the game took a wee while to warm up.
Home midfielder Paul McGowan was the man to get things going on seven minutes when he showed some neat footwork to created space for a cross that was nodded down and wide by Jordon Forster from six yards.
On 10 minutes, the hosts had another go, this time Nelson sending the ball wide of the far post from a tight angle.
The Dark Blues were definitely knocking on the door and it opened for them just a minute later.
The move was started by keeper Conor Hazard, whose clearance upfield reached McGowan. He then played it forward quickly to Hemmings and the striker raced on before finishing expertly with a low, right-foot shot from just inside the box.
Dorrans then landed the ball on the top of the Ayr net when he tried a cheeky chip from outside the area on 15 minutes.
The Honest Men finally made an impression on the game when good play on the left from Scott Tiffoney saw his square the ball to Aaron Drinan, whose first-timed, side-footed shot wasn’t far away.
A netbound Dorrans strike was deflected away for a corner and when Declan McDaid’s kick came over it caused havoc inside the goalmouth as first Christophe Berra’s shot was blocked then Ayr’s Sam Roscoe had to boot the loose ball off the line.
Visiting player Aaron Muirhead was booked for fouling Nelson before the same player came close to equalising on 27 minutes with a header that hit the post. That was the last hurrah for Muirhead, who was replaced by Grant Gillespie on 31 minutes. He had a verbal spat with Dundee boss McPake as he made his way into the dugout.
Hazard then came to the Dark Blues’ rescue minutes later when he dived to save from Tiffoney before, up at the other end, Dundee’s Nelson shot over from 15 yards.
On the stroke of half-time home player Josh Meekings was booked for a challenge on Ayr goalie Ross Doohan.
Two minutes after the restart a sweeping move from the visitors was ended by Stephen Kelly’s half-volley from the edge of the box that flew a foot over the bar.
Dundee’s McDaid then dinked a nice cross on to the head of McGowan, whose flick was saved by Doohan.
On 54 minutes, Hemmings found Nelson with a cutback and, with his back to goal, he managed to turn and shoot but the ball was deflected inches wide for a corner. When the kick came over, Forster headed past.
Ayr player-boss Mark Kerr brought himself on for Connor Malley just after the hour as the visitors searched for a leveller.
McDaid’s corner from the left for the hosts caused havoc inside the opposition goalmouth on 65 minutes and, as the ball bounced up, Nelson’s header was pushed away by Doohan.
Ayr brought on wide player Luke McCowan for the final 20 minutes, while Dundee took off Nelson and replaced him with Crankshaw.
Crankshaw was right in the thick of it on 75 minutes when Hemmings burst down the left wing then played a terrific ball across the face of goal but the sub couldn’t supply the finish and instead went tumbling over diving keeper Doohan.
The Dens men gave Finlay Robertson a chance, replacing McGowan for the latter stages, before Forster had a header cleared off the line by Michael Moffat with nine minutes remaining.
The hosts wrapped it up when a burst forward by Dorrans after a mistake by Ayr boss Kerr saw the Dundee midfielder lay the ball into the path of Crankshaw, who couldn’t miss from six yards.
Dundee: Hazard, Hemmings (Ness 90+2), Forster, Meekings, Berra, Byrne, Nelson (Crankshaw 73), McGowan (Robertson 77), McDaid, Dorrans, Elliot. Subs not used: Sharp, C. Kerr, Field, Cameron.
Ayr United: Doohan, Houston, Moffat, Tiffoney (McCowan 70), Harvie, Muirhead (Gillespie 31), Drinan, Kelly, Roscoe, Malley (M. Kerr 62), Bell. Subs not used: Hare-Reid, Forrest, Docherty, Ecrepont.
Referee: John Beaton.