A terrific long-range strike from their captain Owen Heary and a brace of goals late on from substitute John Burns put Shelbourne safely through to the third round of the FAI Cup.
Workmen's Dunleary certainly lived up to their name as their graft kept Shelbourne at bay throughout the first half.
But there was precious little they could do to keep out Heary's tremendous drive within a minute of the restart. Pat Fenlon's corner was played short to Wes Houlihan who set up Heary. And the left-back let fly with a powerful right-foot shot from 25 yards that found the net after a slight deflection off the head of a defender in a crowded box.
Colin Kelly made a stunning save to keep out a Jim Gannon volley on 66 minutes before his goal was breached again five minutes later.
Burns, on the field just three minutes, chipped home from a Martin Gritton's cross.
Andy McBride ought to have got Workmen's back into the game minutes later when he beat the Shelbourne offside trap but Steve Williams was quickly off his line to save well with his feet.
Burns was through on goal again, this time from Jim Gannon's sublime ball, to finally kill off the Leinster Senior League side nine minutes from time; calmly shooting low past Kelly.
The Dun Laoghaire side availed of some woeful Shelbourne finishing - and a bad miss that might have given them a shock lead - in a scoreless first half.
That miss came on 36 minutes as captain Kelly lifted the siege on his goal with a long kick out. Heary and Tony McCarthy got their wires crossed and Heary slipped as he came to deal with the ball. That let Stephen McBride in one-on-one with Williams. But the midfielder fired low past Williams and wide of the keeper's right hand post.
WORKMEN'S DUNLEARY: Kelly; Brien, O'Connor, Murray, Coffey; Verhoeven (Casey 79), Brown, McDonald, S McBride (Ledwidge 87), Burgess (A McBride 68); Lynch.
SHELBOURNE: Williams; Hutton, Doherty (D. Byrne 50), McCarthy, Heary; Houlihan (Burns 68), Crawford, Gannon, Fenlon, Minnock; Geoghegan (Gritton 59).
Referee: D McKeon (Dublin).